Shadow cabinet finally suffer (4)
I believe the answer is:
tail
'shadow' is the definition.
(both can mean to follow someone)
'cabinet finally suffer' is the wordplay.
'finally' suggests the final letters.
'suffer' becomes 'ail' (ailing is a kind of suffering).
The last letter of 'cabinet' is 't'.
't'+'ail'='TAIL'
(Other definitions for tail that I've seen before include "Elongated appendage of an animal" , "Queue" , "Private investigator" , "Rear appendage of animal" , "private eye" .)