Bitter struggle to take out a cracking spy (10)
I believe the answer is:
astringent
'bitter' is the definition.
(I've seen this before)
'struggle to take out a cracking spy' is the wordplay.
I cannot quite see how this works, but
'take' could be 'string' (stringing is a kind of taking) and 'string' is located in the answer.
'a' is within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for astringent that I've seen before include "Sharp or severe in manner" , "Styptic" , "for checking bleeding" , "medical preparation" , "acerbic" .)