Attach number label to the foot of brown hedge sparrow (7)
I believe the answer is:
dunnock
'hedge sparrow' is the definition.
(synonyms)
'attach number label to the foot of brown' is the wordplay.
I cannot really understand how this works, but
'number' could be 'k' (K is an example) and 'k' is located in the answer.
'of' could be 'o' and 'o' is present in the answer.
'brown' could be 'dun' (dun is a kind of brown) and 'dun' is found within the answer.
The remaining letters 'nc' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dunnock that I've seen before include "Hedge sparrow" , "18's [BIRD]" .)