Fall heavily where hunting party returns (4)
I believe the answer is:
teem
'fall heavily' is the definition.
(I've seen this before)
'hunting party returns' is the wordplay.
'hunting party' becomes 'meet'.
'returns' shows that the letters should be reversed in order.
'meet' backwards is 'TEEM'.
'where' is the link.
(Other definitions for teem that I've seen before include "Be prolific" , "Come down hard" , "(Of rain) pour down" , "stream" , "Bear" .)