Not hard to damage sleeve (3)
I believe the answer is:
arm
'sleeve' is the definition.
('arm' can be a synonym of 'sleeve')
'not hard to damage' is the wordplay.
'not' is a deletion indicator.
'hard' becomes 'h'.
'to damage' becomes 'harm' ('harm' can be a synonym of 'damage').
'harm' with 'h' taken away is 'ARM'.
(Other definitions for arm that I've seen before include "Supply weapons" , "Activate warhead" , "Activate fuse" , "Body part" , "Maybe rifle" .)