Protein in body once developed to limit rising bile (8)
I believe the answer is:
collagen
'protein in body' is the definition.
(collagen is a type of protein in the body)
'once developed to limit rising bile' is the wordplay.
'developed' is an anagram indicator.
'to limit' means one lot of letters goes inside another.
'rising' shows that the letters should be reversed in order (going up in a down clue).
'bile' becomes 'gall' (bile from the gall bladder).
'gall' reversed gives 'llag'.
'once' with letters rearranged gives 'coen'.
'coen' placed around 'llag' is 'COLLAGEN'.
(Other definitions for collagen that I've seen before include "Tough fibrous protein, in skin say" , "Fibrous protein in connective tissue" , "Animal tissue protein" .)