Source of portions of chicken (3)
I believe the answer is:
hen
This clue might be a double definition.
'source' is the first definition.
(I have seen 'Source of eggs ' mean 'hen' so perhaps 'source' could also mean 'hen')
'portions of chicken' is the second definition.
'hen' can be an answer for 'chicken' (hen is a kind of chicken). I am not sure about the 'portions of' bit.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for hen that I've seen before include "Farm bird" , "Domestic egg layer" , "Composed of women" , "Female bird" , "Female lobster, fowl" .)