Official covering English bank (4)
I believe the answer is:
reef
'bank' is the definition.
(thesaurus)
'official covering english' is the wordplay.
'official' becomes 'ref' (match official in football, say).
'covering' indicates putting letters inside.
'english' becomes 'e' (abbreviation).
'ref' enclosing 'e' is 'REEF'.
(Other definitions for reef that I've seen before include "Marine formation" , "Coral structure" , "Hazard for ships" , "The Great Barrier ..., Australian natural wonder" , "Ridge of coral near the sea surface" .)