Military carriers from US roam at sea round Yorkshire resort (8,4)
I believe the answer is:
armoured cars
'military carriers' is the definition.
(military vehicles)
'us roam at sea round yorkshire resort' is the wordplay.
'at sea' is an anagram indicator.
'round' means one lot of letters goes inside another.
'yorkshire resort' becomes 'Redcar' (holiday resort in Yorkshire).
'us'+'roam'='usroam'
'usroam' is an anagram of 'armous'.
'armous' going around 'redcar' is 'ARMOURED CARS'.
'from' acts as a link.
(Another definition for armoured cars that I've seen is " They carry troops".)