A leg, perhaps, of less than sublime form (4)
I believe the answer is:
limb
'a leg perhaps' is the definition.
(leg is a kind of limb)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for limb that I've seen before include "Substantial branch from a tree trunk" , "Eg wing" , "A supporter" , "Large tree branch" , "arm, perhaps" .)