Massive cuckoo feeds little bird, start of contrition? (7)
I believe the answer is:
titanic
'massive' is the definition.
(I've seen this in another clue)
'cuckoo feeds little bird start of contrition?' is the wordplay.
'cuckoo' becomes 'ani' (ani is a kind of cuckoo).
'feeds' means one lot of letters goes inside another (one word is fed by another set of letters).
'little bird' becomes 'tit' (I've seen this in another clue).
'start of' indicates taking the first letters.
The initial letter of 'contrition' is 'c'.
'tit'+'c'='titc'
'ani' put within 'titc' is 'TITANIC'.
(Other definitions for titanic that I've seen before include "Twenty one [SHIP]" , "Giant" , "Having huge strength - ship that famously sunk" , "Of exceptional size or power" , "In act it became an ill-fated ship" .)