Turn circles around a friend? Of course (9)
I believe the answer is:
naturally
'of course' is the definition.
('naturally' can be a synonym of 'of course')
'turn circles around a friend?' is the wordplay.
'circles' indicates anagramming the letters.
'around' is an insertion indicator.
'friend?' becomes 'ally' ('ally' can be a synonym of 'friend'**).
'turn' is an anagram of 'ntur'.
'ntur' placed around 'a' is 'natur'.
'natur'+'ally'='NATURALLY'
(Other definitions for naturally that I've seen before include "Occurring normally, not artificially" , "without medical assistance" , "Without affectation" , "Without artificial help" , "as anticipated" .)