Very black blubber (3)
I believe the answer is:
sob
'blubber' is the definition.
(I've seen this before)
'very black' is the wordplay.
'very' becomes 'so' (I've seen this in other clues).
'black' becomes 'b' (as in pencil classifications).
'so'+'b'='SOB'
(Other definitions for sob that I've seen before include "Blubber" , "making one gasp" , "Weep uncontrollably" , "Weeping gasp" , "Snivel" .)