Home bird builds above a girl (5)
I believe the answer is:
nesta
'girl' is the definition.
(I know that Nesta is a female given name)
'home bird builds above a' is the wordplay.
'home bird builds' becomes 'nest' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'above' says to put letters next to each other (in a down clue, some letters go above others).
'nest'+'a'='NESTA'
Can you help me to learn more?
(Other definitions for nesta that I've seen before include "woman" , "girl" .)