Pal lacking a prominent feature (4)
I believe the answer is:
chin
'prominent feature' is the definition.
(I've seen this before)
'pal lacking a' is the wordplay.
'pal' becomes 'china' (china plate is Cockney rhyming slang for mate).
'lacking' is a deletion indicator.
'china' with 'a' taken away is 'CHIN'.
(Other definitions for chin that I've seen before include "Front of lower jaw" , "What's repeatedly required for a toast" , "hit" , "Part of the face (on which one may have to take it?)" , "Inch (anag.)" .)