Surf for missing Romeo, American (4)
I believe the answer is:
foam
'surf' is the definition.
(thesaurus)
'for missing romeo american' is the wordplay.
'missing' suggests deleting specific letters.
'romeo' becomes 'R' (phonetic alphabet: alpha, bravo, charlie etc.).
'american' becomes 'Am' (abbreviation in some contexts).
'for' with 'r' removed is 'fo'.
'fo'+'am'='FOAM'
(Other definitions for foam that I've seen before include "At the mouth, this may mean madness or extreme anger" , "Lather, froth" , "Boiling bubbles" , "Froth created by wave or soap" , "Fizz, froth" .)