The turn is interrupted by a performer (8)
I believe the answer is:
thespian
'performer' is the definition.
(I know that thespian is a type of performer)
'the turn is interrupted by a' is the wordplay.
'turn' becomes 'spin' (spin is a kind of turn).
'is interrupted by' is an insertion indicator.
'spin' going around 'a' is 'spian'.
'the'+'spian'='THESPIAN'
(Other definitions for thespian that I've seen before include "Relating to the theatre" , "Tree, say" , "Theatrical type" , "person in the acting business" , "Actor - neat hips (anag)" .)