Let go of ambition to deliver score (4,4)
I believe the answer is:
drop goal
'score' is the definition.
(I've seen this before)
'let go of ambition' is the wordplay.
'let go of' becomes 'drop' (I've seen this in another clue).
'ambition' becomes 'goal' (I've seen this before).
'drop'+'goal'='DROP-GOAL'
'to deliver' is the link.
(Other definitions for drop goal that I've seen before include "score points?" , "One way of scoring at rugby" , "one scores with over the bar" .)