Pears can affect body part (8)
I believe the answer is:
pancreas
'body part' is the definition.
('pancreas' is part of 'body')
'pears can affect' is the wordplay.
'affect' indicates an anagram (I've seen 'affecting' mean this).
'pears'+'can'='pearscan'
'pearscan' anagrammed gives 'PANCREAS'.
(Other definitions for pancreas that I've seen before include "Gland secreting digestive enzymes" , "It secretes insulin" , "Gland aiding digestion" , "secreting structure" , "insulin producer" .)