Organise a turn by friend, of course (9)
I believe the answer is:
naturally
'of course' is the definition.
(synonyms)
'organise a turn by friend' is the wordplay.
'organise' is an anagram indicator.
'by' says to put letters next to each other.
'friend' becomes 'ally' (an ally is a friend or supporter).
'a'+'turn'='aturn'
'aturn' is an anagram of 'natur'.
'natur'+'ally'='NATURALLY'
(Other definitions for naturally that I've seen before include "as you might expect" , "Occurring normally, not artificially" , "In an artless way" , "as normal" , "without medical assistance" .)