Impressed by English dash (8)
I believe the answer is:
stampede
'dash' is the definition.
(thesaurus)
'impressed by english' is the wordplay.
'impressed' becomes 'stamped' (stamping is a kind of impressing).
'by' means one lot of letters go next to another.
'english' becomes 'e' (abbreviation).
'stamped'+'e'='STAMPEDE'
(Other definitions for stampede that I've seen before include "Wild run of frightened cattle" , "Headlong rush of animals" , "rush for safety maybe" , "Pasted me (anag.)" , "Panicked rush (of cattle)" .)