Pioneer dog jacket (11)
I believe the answer is:
trailblazer
'pioneer' is the definition.
(I know that pioneer can be written as trailblazer)
'dog jacket' is the wordplay.
'dog' becomes 'trail' (both can mean to follow).
'jacket' becomes 'blazer' (blazer is a kind of jacket).
'trail'+'blazer'='TRAILBLAZER'
(Other definitions for trailblazer that I've seen before include "trendsetter" , "Leader in the field" , "Pioneer, innovator" .)