In half a hour she becomes an attendant (5)
I believe the answer is:
usher
'an attendant' is the definition.
(usher is a kind of attendant)
'in half a hour she' is the wordplay.
'in' means one lot of letters goes inside another.
'half a' means to take half the letters.
'hour' with half the letters taken is 'ur'.
'ur' enclosing 'she' is 'USHER'.
'becomes' acts as a link.
(Other definitions for usher that I've seen before include "Person who shows one to a seat" , "Person whose job is to conduct others" , "Theatre/cinema worker" , "Guide at wedding" , "Theatre attendant" .)