Audible sound of farmyard animal close by makes one more dreamy (7)

'more dreamy' is the definition.
('moony' can be a synonym of 'dreamy')

'audible sound of farmyard animal close by makes one' is the wordplay.
I cannot quite understand how this works, but
'sound' could be 'moo' (moo is a kind of sound) and 'moo' is present in the answer.
'one' could be 'i' (Roman numeral) and 'i' is found in the answer.
This explanation may well be incorrect...