Deliberately (2,7)
I believe the answer is:
on purpose
'deliberately' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for on purpose that I've seen before include "Deliberately, intentionally" , "Pours open - quite deliberately (2,7)" , "Deliberately, not by chance" , "Oppose run with deliberate intention" , "Deliberately, with full intent" .)