We must support English lamb producer (3)
I believe the answer is:
ewe
'lamb producer' is the definition.
(I've seen this in another clue)
'we must support english' is the wordplay.
'must support' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'english' becomes 'E' (abbreviation as in OED).
'we' after 'e' is 'EWE'.
(Other definitions for ewe that I've seen before include "A palindromic sheep" , "She'll provide material to knit" , "Female ovine" , "Female on farm" , "Farm animal" .)