Girl is in time (5)
I believe the answer is:
daisy
'girl' is the definition.
'is in time' is the wordplay.
'in' means one lot of letters goes inside another.
'time' becomes 'day' (day is a kind of time).
'is' going inside 'day' is 'DAISY'.
(Other definitions for daisy that I've seen before include "Common wild flower" , "Grassland plant" , "bloomer" , "Flower of lawn and meadow" , "Composite" .)