Confine the poor critters (8)
I believe the answer is:
restrict
'confine' is the definition.
(restricting is a kind of confining)
'the poor critters' is the wordplay.
'the poor' is an anagram indicator.
'critters' with letters rearranged gives 'RESTRICT'.
(Other definitions for restrict that I've seen before include "Check" , "Confine within limits" , "hamper" , "Deprive of freedom" , "Keep under control" .)