Beer up? That’s fine! (5)
I believe the answer is:
regal
'fine' is the definition.
(thesaurus)
'beer up?' is the wordplay.
'beer' becomes 'lager' (lager is a kind of beer).
'up?' is a reversal indicator (in down clue: letters go upwards).
'lager' reversed gives 'REGAL'.
'that's' is the link.
(Other definitions for regal that I've seen before include "King's" , "befitting a king" , "Fit for a king" , "Like a queen?" , "King-like" .)