Trendy? That girl must be with it to take over (7)
I believe the answer is:
inherit
'take over' is the definition.
(take ownership of something)
'trendy? that girl must be with it' is the wordplay.
'trendy?' becomes 'in' ('in' can mean fashionable).
'that girl' becomes 'her' ('her' refers to a girl or woman).
'must be with' says to put letters next to each other.
'in'+'her'+'it'='INHERIT'
'to' acts as a link.
(Other definitions for inherit that I've seen before include "Come into (money)" , "Receive from a deceased parent" , "Be the recipient of" , "Benefit from willing" , "Be left with (a situation)" .)