Rear is fine part of the body (4)
I believe the answer is:
farm
'rear' is the definition.
(thesaurus)
'fine part of the body' is the wordplay.
I cannot really understand how this works, but
'fine' could be 'f' (abbreviation) and 'f' is found in the answer.
'part' could be 'arm' (arm is a kind of part) and 'arm' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'is' acts as a link.
Can you help me to learn more?
(Other definitions for farm that I've seen before include "Agricultural dwelling" , "Smallholding" , "Manage land for crops or livestock" , "Cultivate the land" , "Land used for cultivation" .)