Ordering a pint is not appropriate (5)
I believe the answer is:
inapt
'not appropriate' is the definition.
(inapt means inappropriate or ill-fitting)
'ordering a pint' is the wordplay.
'ordering' indicates an anagram.
'a'+'pint'='apint'
'apint' anagrammed gives 'INAPT'.
'is' acts as a link.
(Other definitions for inapt that I've seen before include "unqualified" , "Unsuited" , "Improper" , "Not fitting" , "badly judged" .)