Traditional site for an engagement? (11)
I believe the answer is:
'traditional site for an engagement?' is the definition.
(as in a military engagement)
'traditional site for an engagement?' is the wordplay.
'traditional site' becomes 'field' (I can't explain this - if you can you should believe this answer much more).
'for' means one lot of letters go next to another (I've seen this in other clues).
'an engagement?' becomes 'battle' (synonyms).
'field' put after 'battle' is 'BATTLEFIELD'.
(Other definitions for battlefield that I've seen before include "Scene of conflict", "Place of conflict", "Scene of military action", "arena", "situation demanding firepower".)