This girl sound in the pink (5)
I believe the answer is:
rosie
'this girl' is the definition.
(girl's name)
'sound in the pink' is the wordplay.
'sound' becomes 'i' (I can't justify this - if you can you should believe this answer much more).
'in the' means one lot of letters goes inside another.
'pink' becomes 'rose' (colour).
'i' placed inside 'rose' is 'ROSIE'.
Can you help me to learn more?
(Other definitions for rosie that I've seen before include "Cider with --, novel" , "Cider with - (Laurie Lee)" , "Female" , "riveting woman in 40s?" , "cider drinker sounds red" .)