Gather English literature must be rejected as barren (9)
I believe the answer is:
infertile
'barren' is the definition.
(synonyms)
'gather english literature must be rejected' is the wordplay.
'gather' becomes 'infer' (synonyms).
'english' becomes 'E' (abbreviation).
'literature' becomes 'lit'.
'must be rejected' says the letters should be written backwards.
'e'+'lit'='elit'
'elit' reversed gives 'tile'.
'infer'+'tile'='INFERTILE'
'as' acts as a link.
(Other definitions for infertile that I've seen before include "Not productive" , "Fruitless" , "Barren" , "So can't father" .)