Naive pub with round coin (8)
I believe the answer is:
innocent
'naive' is the definition.
(similar in meaning)
'pub with round coin' is the wordplay.
'pub' becomes 'inn' (an inn is a type of pub).
'with' means one lot of letters go next to another.
'round' becomes 'o' (round can mean a round object).
'coin' becomes 'cent' (cent is a kind of coin).
'inn'+'o'+'cent'='INNOCENT'
(Other definitions for innocent that I've seen before include "otherworldly?" , "Pope" , "Harmless or guiltless" , "Guiltless or guileless" , "Artless or guiltless" .)