Loses possession of illegally gained ball, landing at back of net (4,4)
I believe the answer is:
drop shot
'illegally gained ball landing at back of net' is the definition.
I can't judge whether this defines the answer.
'loses possession' is the wordplay.
'loses' becomes 'drops' (dropping is a kind of losing).
'possession' becomes 'hot' (I can't explain this - if you can you should believe this answer much more).
'drops'+'hot'='DROP-SHOT'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for drop shot that I've seen before include "Hit (in tennis, squash) awkward to return" , "strong highball? Hardly" , "One may land in court" , "Stroke" .)