Porridge that is part of course done well (6)
I believe the answer is:
birdie
'part of course done well' is the definition.
(a hole, part of a golf course)
'porridge that is' is the wordplay.
'porridge' becomes 'bird' (I've seen this before).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'bird'+'ie'='BIRDIE'
(Other definitions for birdie that I've seen before include "Golfing score better than par" , "In golf, a score of one under par for the hole" , "low score" , "One under in 20 across" , "One under par - watch it!" .)