Sports field - in Red Square naturally (5)
I believe the answer is:
arena
'sports field' is the definition.
'arena' can be an answer for 'field' (arena is a kind of field). I'm not certain of the 'sports' bit.
'in red square naturally' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ARENA' is hidden within 'red square naturally'.
Can you help me to learn more?
(Other definitions for arena that I've seen before include "Wembley, for example" , "The place of action" , "domain" , "Ring; stadium" , "Place of combat" .)