Rational soldier in pub (7)
I believe the answer is:
logical
'rational' is the definition.
(associated in meaning)
'soldier in pub' is the wordplay.
'soldier' becomes 'GI' (term for US soldier).
'in' means one lot of letters goes inside another.
'pub' becomes 'local' (one's local pub).
'gi' put into 'local' is 'LOGICAL'.
(Other definitions for logical that I've seen before include "Consistent with reason" , "Well thought out" , "clear" , "According with reason" , "Clearly and soundly reasoned" .)