Dog with dog lead evenly trimmed (9)
I believe the answer is:
curtailed
'trimmed' is the definition.
(thesaurus)
'dog with dog lead evenly' is the wordplay.
'dog' becomes 'cur' (cur is a kind of dog).
'with' says to put letters next to each other.
'dog' becomes 'tail' ('tail' can be a synonym of 'dog'**).
'evenly' means one should take alternating letters (even-numbered letters only).
The alternate letters of 'lead' are 'ed'.
'cur'+'tail'+'ed'='CURTAILED'
(Other definitions for curtailed that I've seen before include "Clipped" , "Reduced" , "Broken off" , "docked" , "Made short" .)