Trophy battle constrained by a draw's opening (5)
I believe the answer is:
award
'trophy' is the definition.
(I've seen this before)
'battle constrained by a draw's opening' is the wordplay.
'battle' becomes 'war' (I've seen this in other clues).
'constrained by' indicates putting letters inside.
'opening' suggests taking the first letters.
The initial letter of 'draws' is 'd'.
'a'+'d'='ad'
'war' inserted inside 'ad' is 'AWARD'.
(Other definitions for award that I've seen before include "Perhaps Tony" , "Decoration" , "Present - prize" , "Tony, for example" , "E.g. Oscar" .)