As with all cryptic clues there will be a definition and a secondary indicator. The secondary indicator will contain a word or words in which the answer is hidden and information that tells you where to look. Often this information is just the word 'in' or 'of'. As in these simple hidden word clues:
6. Conjunction of landslides (3)
6. Scarcity from blackness (4)
6. Finishes in Friendship (4)
6. Number of weights (5)
6. Gun sheath in upholstery (7)
These are the simplest of hidden word clues because the hidden word is hidden entirely within one other word and you can hear the hidden word when you read the clue aloud (with the possible exception of 'ENDS' in 'friendship' for any phoneticians that are reading). A level of elegance can be added by hiding the answer in a word that shares the letters but not the sound of the word. An effective way of doing this is to stretch the solution across two words.
6. Unity in honesty (3)
6. Look for wire in hearthside (5)
6. Flesh of some atheists (4)
6. Beginnings of Kangaroo Tsar (5)
In a quick crossword, a clue such as:
6. One of the seven Pleiades (7)
is essentially unsolvable without a reference book.
But a cryptic can give you a fairer chance to get to an obscure word by making it a hidden word clue:
6. One of seven sisters seen in hipster open-day (7)
This clue does not require you to know the names of the sisters from Greek Mythology. If you can identify the clue as a hidden word clue, then a couple of crossing letters in the grid should enable you to make a reasonable guess.
Finally and fiendishly, all of the above can apply to Reversals - answers hidden back to front. Look for indicators that you should read part of a word or words backwards. Have a go at these:
6. Cover back in Antediluvian shelter (3)
6. Joint returns from seen kindness (4)
6. Delphiniums in a growbag that, viewed from a particular direction, contains something living (8)