A clever trick that comes with care perhaps (7)
I believe the answer is:
wrinkle
'care perhaps' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for wrinkle that I've seen before include "Depression in the smoothness of a surface, skin perhaps" , "Furrow, crease" , "Age line" , "Valuable hint - handy dodge" , "Minor difficulty" .)