Conceals mysteries about English (8)
I believe the answer is:
secretes
'conceals' is the definition.
(both can mean to hide)
'mysteries about english' is the wordplay.
'mysteries' becomes 'secrets' (I've seen this before).
'about' indicates putting letters inside.
'english' becomes 'E' (abbreviation).
'secrets' enclosing 'e' is 'SECRETES'.
(Other definitions for secretes that I've seen before include "Hides away" , "Conceals, hides" , "Places out of sight" .)