Sound of soldier in pub (7)
I believe the answer is:
logical
'sound' is the definition.
(I've seen this before)
'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' going inside 'local' is 'LOGICAL'.
'of' is the link.
(Other definitions for logical that I've seen before include "Well thought out" , "Deducible" , "According with reason" , "In accordance with reason" , "clear" .)