Companion comes in always feeling pained (4)
I believe the answer is:
achy
'feeling pained' is the definition.
'companion comes in always' is the wordplay.
'companion' becomes 'ch' (I've seen this in other clues).
'comes in' is an insertion indicator.
'always' becomes 'ay'.
'ch' inserted within 'ay' is 'ACHY'.
(Other definitions for achy that I've seen before include "Giving pain" , "Suffering from dull pains" , "Dully painful" , "Persistently painful" , "Continuously painful" .)