But it's not the only bird that settles for the night (7)
I believe the answer is:
rooster
'bird that settles for the night' is the definition.
'rooster' can be an answer for 'bird' (rooster is a kind of bird). I am unsure of the remainder of the definition.
'but it's not the only' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'it' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rooster that I've seen before include "Adult male chicken" , "American cockerel" , "One may crow" , "Chanticleer" , "Farmyard fowl" .)