Inflamed area poked by sick fool (7)
I believe the answer is:
pillock
'fool' is the definition.
(pillock can mean a foolish person)
'inflamed area poked by sick' is the wordplay.
'inflamed area' becomes 'pock' (mark on skin).
'poked by' indicates putting letters inside (inserted letters poke into others).
'sick' becomes 'ill' (similar in meaning).
'pock' enclosing 'ill' is 'PILLOCK'.
(Other definitions for pillock that I've seen before include "clot" , "Fool (slang)" .)