Northern beer served up in style (4)
I believe the answer is:
elan
'style' is the definition.
(I know that style can be written as elan)
'northern beer served up' is the wordplay.
'northern' becomes 'n' (abbreviation e.g. N. Ireland).
'beer' becomes 'ale' (type of beer).
'served up' is a reversal indicator (in a down clue, going upwards).
'n'+'ale'='nale'
'nale' back-to-front is 'ELAN'.
'in' is the link.
(Other definitions for elan that I've seen before include "Vivacity, dash" , "Stylish enthusiasm" , "Dash, style" , "Combination of style and vigour" , "Dashing style" .)