Sea bed may be made lower (6)
I believe the answer is:
debase
'lower' is the definition.
(I've seen this before)
'sea bed may be' is the wordplay.
'may be' indicates anagramming the letters.
'sea'+'bed'='seabed'
'seabed' is an anagram of 'DEBASE'.
'made' acts as a link.
(Other definitions for debase that I've seen before include "Lower -- seabed (anag)" , "Lower in value or quality, sometimes currency" , "Degrade or devalue" , "Lower the character of" , "Lower in quality or value, corrupt" .)