Drink, tea to begin with, behind sandwiches? (5)
I believe the answer is:
latte
'drink' is the definition.
(type of coffee drink)
'tea to begin with behind sandwiches?' is the wordplay.
'to begin with' suggests taking the first letters.
'behind' becomes 'late' (as in behind schedule).
'sandwiches?' means one lot of letters goes inside another (goes on either side like a sandwich).
The initial letter of 'tea' is 't'.
't' inserted into 'late' is 'LATTE'.
(Other definitions for latte that I've seen before include "Kind of espresso coffee" , "See 21" , "Style of coffee" , "Type of coffee" , "Coffee served with hot milk" .)