Set up tent -- coitus unfolds (10)
I believe the answer is:
constitute
'set up' is the definition.
(thesaurus)
'tent coitus unfolds' is the wordplay.
'unfolds' is an anagram indicator (I've seen 'unfolding' mean this (untangle or unfold the original letter order)).
'tent'+'coitus'='tentcoitus'
'tentcoitus' is an anagram of 'CONSTITUTE'.
(Other definitions for constitute that I've seen before include "form" , "Be (a part) of a whole" , "Make up" , "Found" .)