Whale fat (7)
I believe the answer is:
blubber
'whale fat' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for blubber that I've seen before include "Break down" , "Cry uncontrollably" , "Fat of sea mammals - cry" , "Layer of fat under the skin of whales" , "Sob bitterly" .)