Of course, all holes circular (5)
I believe the answer is:
round
I believe this clue is a double definition.
'of course all holes' is the first definition.
(all the holes on a golf course)
'circular' is the second definition.
(synonyms)
(Other definitions for round that I've seen before include "balls are like this" , "A single shot" , "Set of drinks; song" , "18 holes of golf" , "(Of voice) rich, mellow" .)