Joe's in the pub, as is reasonable (7)
I believe the answer is:
logical
'is reasonable' is the definition.
(similar in meaning)
'joe's in the pub' is the wordplay.
'joe' becomes 'gi' (GI Joe).
'in' means one lot of letters goes inside another.
'the pub' becomes 'local' (I've seen this before).
'gi' placed inside 'local' is 'LOGICAL'.
'as' acts as a link.
(Other definitions for logical that I've seen before include "Objective" , "Showing rational thought" , "Well-reasoned" , "entirely reasonable" , "Consistent with reason" .)