Restrict dog following dog (7)
I believe the answer is:
curtail
'restrict' is the definition.
('curtail' can be a synonym of 'restrict')
'dog following dog' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'following' says to put letters next to each other.
'dog' becomes 'tail' ('tail' can be a synonym of 'dog'**).
'cur'+'tail'='CURTAIL'
(Other definitions for curtail that I've seen before include "Reduce in extent" , "Impose a restriction on" , "Cut short (an activity)" , "Reduce in length" , "Cut short like canine appendage" .)