Lift second whale (8)
I believe the answer is:
humpback
'whale' is the definition.
(I know that humpback is a type of baleen whale)
'lift second' is the wordplay.
'lift' becomes 'hump' (hump can mean to lift or carry with difficulty).
'second' becomes 'back' (to second a motion is to back it).
'hump'+'back'='HUMPBACK'
(Other definitions for humpback that I've seen before include "Handicap" , "Type of whale" , "Whale - kind of bridge" , "Variety of whale or bridge" .)