Rich person with unlimited beer — sweet! (6)
I believe the answer is:
toffee
'sweet' is the definition.
(I know that toffee is a type of sweet)
'rich person with unlimited beer' is the wordplay.
'rich person' becomes 'toff' (toff is a kind of rich person).
'with' means one lot of letters go next to another.
'unlimited' says to take the centre (discard the edges or 'limits' of the word).
The middle of 'beer' is 'ee'.
'toff'+'ee'='TOFFEE'
(Other definitions for toffee that I've seen before include "Chewy confection" , "That could be tough to swallow" , "Chewy sweet" , "Sticky sweet" , "Hard-to-chew sweet" .)