Almost aiming for painkiller (7)
I believe the answer is:
aspirin
'for painkiller' is the definition.
(aspirin is a kind of painkiller)
'almost aiming' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'aiming' becomes 'aspiring' ('aspire' can be a synonym of 'aim').
'aspiring' with its final letter removed is 'ASPIRIN'.
(Other definitions for aspirin that I've seen before include "Sip rain (anag.)" , "Anodyne" , "Pain relief" , "Anti-inflammatory drug" , "answer to pain?" .)