Girl from the United States missing mother on the way up (5)
I believe the answer is:
erica
'girl' is the definition.
(I've seen this before)
'the united states missing mother on the way up' is the wordplay.
'the united states' becomes 'america' ('America' can be a synonym of 'united states').
'missing' indicates named letters should be taken away.
'mother' becomes 'ma' (ma is a kind of mother).
'on the way up' shows that the letters should be reversed in order.
'ma' written backwards gives 'am'.
'america' with 'am' removed is 'ERICA'.
'from' acts as a link.
(Other definitions for erica that I've seen before include "Shrub genus; girl's name" , "Girl's name - I care (anag)" , "I care about Heather, oddly" , "Girl - heather" , "found on the moors" .)