Detailed description is about English type (7)
I believe the answer is:
species
'type' is the definition.
(I've seen this before)
'detailed description is about english' is the wordplay.
'detailed description' becomes 'spec' (I've seen this in another clue).
'about' indicates putting letters inside.
'english' becomes 'E' (abbreviation).
'is' enclosing 'e' is 'ies'.
'spec'+'ies'='SPECIES'
(Other definitions for species that I've seen before include "Groups of related plants or animals" , "Sort, type" , "Kind of creature" , "Biological group" , "Breed or genus" .)