Host Romeo in skimpy beachwear (6)
I believe the answer is:
throng
'host' is the definition.
(both can mean a large group of people)
'romeo in skimpy beachwear' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'in' means one lot of letters goes inside another.
'skimpy beachwear' becomes 'thong' (I've seen this in another clue).
'r' put into 'thong' is 'THRONG'.
(Other definitions for throng that I've seen before include "Multitude" , "Large numbers" , "Troop" , "Milling crowd" , "Mob" .)