Countryman joining politician at port in bed (10)
I believe the answer is:
compatriot
'countryman' is the definition.
(synonyms)
'joining politician at port in bed' is the wordplay.
'joining' says to put letters next to each other.
'politician' becomes 'mp' (Member of Parliament).
'port' becomes 'rio' (Rio de Janeiro is a port).
'in' means one lot of letters goes inside another.
'bed' becomes 'cot' (cot is a kind of bed).
'mp'+'at'='mpat'
'mpat'+'rio' is 'mpatrio'.
'mpatrio' put within 'cot' is 'COMPATRIOT'.
(Another definition for compatriot that I've seen is " Fellow citizen".)