Feed scruffy gull, daily at first - it will fly off when grown up (5,7)
I believe the answer is:
fully fledged
'up' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?
'feed scruffy gull daily at first it will fly off when grown' is the wordplay.
I cannot really see how this works, but
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
'will' could be 'll' (contracted form, as in 'he'll' - 'he will') and 'll' is found in the answer.
an anagram of 'fly' is 'yfl' which is located in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for fully fledged that I've seen before include "In finished state; ready to fly" , "Completely developed" , "leave home for a lark?" , "Mature" .)