Girl and American pal making bloomer (7)
I believe the answer is:
rosebud
'bloomer' is the definition.
(I've seen this before)
'girl and american pal' is the wordplay.
'girl' becomes 'rose' ().
'and' means one lot of letters go next to another.
'american pal' becomes 'bud' (US term for a friend).
'rose'+'bud'='ROSEBUD'
'making' acts as a link.
(Other definitions for rosebud that I've seen before include "Partially-opened flower" , "Bored us (anag.)" , "J. Foster Kane's last word" , "Young flower (to be gathered?)" , "one with potential to bloom" .)