Part of leg in small 3, say (4)
I believe the answer is:
calf
This could be a double definition.
'part' is the first definition.
(calf is a kind of part)
'leg in small 3 say' is the second definition.
'calf' can be an answer for 'leg' (thesaurus). I am not sure about the 'in small 3 say' bit.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for calf that I've seen before include "Fine leather - young whale" , "Young bovine animal" , "Animal that yields veal" , "Young moo-er" , "Young animal; part of body" .)