The beer on the right is active (5)
I believe the answer is:
alert
'active' is the definition.
(thesaurus)
'the beer on the right' is the wordplay.
'the beer' becomes 'ale' (I've seen this before).
'on' says to put letters next to each other.
'the right' becomes 'rt'.
'ale'+'rt'='ALERT'
'is' is the link.
(Other definitions for alert that I've seen before include "Watchfully awake" , "Watchful and observant" , "Vigilantly attentive" , "alarm" , "On one's toes" .)