Pub in the right to get less stout (7)
I believe the answer is:
thinner
'less stout' is the definition.
'pub in the right' is the wordplay.
'pub' becomes 'inn' (I've seen this before).
'in' is an insertion indicator.
'right' becomes 'r' (common abbreviation).
'inn' put inside 'the' is 'thinne'.
'thinne'+'r'='THINNER'
'to get' is the link.
(Other definitions for thinner that I've seen before include "More runny" , "Finer; turps, e.g." , "Volatile liquid" , "Dissoving agent" , "Solvent; less thick" .)