Silver coin Mike found in kingdom (5)
I believe the answer is:
realm
'kingdom' is the definition.
(I've seen this before)
'silver coin mike' is the wordplay.
'silver coin' becomes 'real' (Spanish real).
'mike' becomes 'M' (phonetic alphabet: alpha, bravo, charlie etc.).
'real'+'m'='REALM'
'found in' acts as a link.
(Other definitions for realm that I've seen before include "Peers are possessed by this" , "the UK, perhaps" , "Empire - state" , "Knowledge base" , "World" .)