Dairy product a girl takes in bed (7)
I believe the answer is:
ricotta
'dairy product' is the definition.
(ricotta is a kind of dairy product)
'a girl takes in bed' is the wordplay.
'a girl' becomes 'rita' (**).
'takes in' indicates putting letters inside.
'bed' becomes 'cot' (cot is a kind of bed).
'rita' enclosing 'cot' is 'RICOTTA'.
(Other definitions for ricotta that I've seen before include "Italian 8 across" , "Cheese - Riot Act (anag)" , "may be served with biscuits" , "Ital. cheese" , "one brought on board?" .)