Howl like a huge mammal, say (4)
I believe the answer is:
wail
'howl' is the definition.
('wail' can be a synonym of 'howl')
'a huge mammal say' is the wordplay.
'a huge mammal' becomes 'whale' (I've seen this before).
'say' indicates a 'sounds like' (homophone) clue.
'whale' sounds like 'WAIL'.
'like' acts as a link.
(Other definitions for wail that I've seen before include "Whimper" , "Sorrowful cry" , "Long cry, sounds like cetacean" , "Cry of grief" , "Prolonged cry" .)