Bill attends hospital with injury, ultimately it's painful (4)
I believe the answer is:
achy
'painful' is the definition.
(similar in meaning)
'bill attends hospital with injury ultimately' is the wordplay.
'bill' becomes 'ac' (short for account).
'attends' means one lot of letters go next to another.
'hospital' becomes 'h' (abbreviation for hospital on maps).
'with' means one lot of letters go next to another.
'ultimately' suggests the final letters.
The last letter of 'injury' is 'y'.
'ac'+'h'+'y'='ACHY'
'it's' is the link.
(Other definitions for achy that I've seen before include "Persistently painful" , "Feeling in need of an aspirin?" , "suffering dull pain" , "Dully painful" , "Suffering from dull pains" .)