I see through play that's going round in circles (7)
I believe the answer is:
tropics
'circles' is the definition.
(I know this)
'i see through play that's going round' is the wordplay.
'see' becomes 'C' (the word for the letter, according to Chambers).
'through' indicates putting letters inside (inserted letters go through the word).
'play' becomes 'sport' (sporting is a kind of playing).
'that's going round' says the letters should be written in reverse.
'sport' in reverse letter order is 'trops'.
'i'+'c'='ic'
'ic' placed inside 'trops' is 'TROPICS'.
'in' acts as a link.
(Other definitions for tropics that I've seen before include "hot regions" , "Cancer, Capricorn" , "Region either side of equator" , "hot spot" , "hot spots" .)