Having sex in May ruined friendship (5)
I believe the answer is:
amity
'friendship' is the definition.
(I've seen this before)
'having sex in may ruined' is the wordplay.
I cannot really see how this works, but
'sex' could be 'it' (a common euphemism) and 'it' is found in the answer.
an anagram of 'may' is 'amy' which is located in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for amity that I've seen before include "Friendly feeling, fraternity" , "Cordial friendship" , "Fellowship" , "understanding" , "Friendliness" .)