Superficial sea foam expert (7)
I believe the answer is:
surface
'superficial' is the definition.
(similar in meaning)
'sea foam expert' is the wordplay.
'sea foam' becomes 'surf' (I've seen this before).
'expert' becomes 'ace' (ace is a kind of expert).
'surf'+'ace'='SURFACE'
(Other definitions for surface that I've seen before include "In water, come to the top" , "Uppermost layer" , "Worktop" , "Outside part" , "skin" .)