Set about including a surfeit (4)
I believe the answer is:
sate
'surfeit' is the definition.
(thesaurus)
'set about including a' is the wordplay.
'about' indicates anagramming the letters.
'including' is an insertion indicator.
'set' is an anagram of 'ste'.
'ste' enclosing 'a' is 'SATE'.
(Other definitions for sate that I've seen before include "Satisfy to excess" , "Supply too much" , "Satisfy completely" , "Malaysian dish" , "Overfill, gorge" .)