Outstanding! Girl picked up an escort (6)
I believe the answer is:
duenna
'an escort' is the definition.
(I've seen this before)
'outstanding girl picked up' is the wordplay.
'outstanding' becomes 'due' (I've seen this before).
'girl' becomes 'ann' (woman's name).
'picked up' shows that the letters should be reversed in order.
'ann' reversed gives 'nna'.
'due'+'nna'='DUENNA'
(Other definitions for duenna that I've seen before include "mature escort" , "Woman chaperon in Hispanic countries" , "Female chaperone" , "Governess, chaperone" , "Spanish chaperon or governess" .)