Impeded deer? Poor deer! (8)
I believe the answer is:
hindered
'impeded' is the definition.
('hinder' can be a synonym of 'impede')
'deer? poor deer' is the wordplay.
'deer?' becomes 'hind' (hind is a kind of deer).
'poor' indicates an anagram.
'deer' anagrammed gives 'ered'.
'hind'+'ered'='HINDERED'
(Other definitions for hindered that I've seen before include "Impeded" , "Kept back by delaying progress" , "Obstructed - delayed" , "Kept back, hampered" , "Hampered, obstructed" .)