Dock where dog follows rat (7)
I believe the answer is:
curtail
'dock' is the definition.
(I've seen this in another clue)
'dog follows rat' is the wordplay.
'dog' becomes 'cur' (a cur is an aggressive or scruffy dog).
'follows' says to put letters next to each other.
'rat' becomes 'tail' (I can't justify this - if you can you should give a lot more credence to this answer).
'cur'+'tail'='CURTAIL'
'where' is the link.
Can you help me to learn more?
(Other definitions for curtail that I've seen before include "Cut short (an activity)" , "Reduce in length" , "Dock" , "Shorten, abridge" , "Cut short like canine appendage" .)