To leave, in any case, can mean torment (5)
I believe the answer is:
agony
'torment' is the definition.
(synonyms)
'to leave in any' is the wordplay.
'to leave' becomes 'go' (both can mean to depart).
'in' means one lot of letters goes inside another.
'go' placed inside 'any' is 'AGONY'.
'case can mean' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for agony that I've seen before include "Really severe pain" , "sort of aunt" , "This aunt answers readers' questions" , "woe" , "Mental suffering" .)