Anchor possibly thrown in wide English river (11)
I believe the answer is:
broadcaster
'anchor possibly' is the definition.
(anchor can mean a lead presenter)
'thrown in wide english river' is the wordplay.
'thrown' becomes 'cast' (I've seen this before).
'in' indicates putting letters inside.
'wide' becomes 'broad' (synonyms).
'english' becomes 'e' (abbreviation).
'river' becomes 'r' (abbreviation for river).
'broad'+'e'='broade'
'cast' put inside 'broade' is 'broadcaste'.
'broadcaste'+'r'='BROADCASTER'
(Other definitions for broadcaster that I've seen before include "Radio or TV journalist" , "radio station" , "Radio/TV provider" .)