Dock dog after dog (7)
I believe the answer is:
curtail
'dock' is the definition.
(I've seen this before)
'dog after dog' is the wordplay.
'dog' becomes 'cur' (I've seen this before).
'after' 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 length" , "make shorter" , "Cut short like canine appendage" , "Abbreviate" , "Dock" .)