Very short dog with a trouble-free tail! (4)
I believe the answer is:
curt
'very short' is the definition.
'curt' can be an answer for 'short' (impolite). I am unsure of the 'very' bit.
'dog with a trouble-free tail' is the wordplay.
'dog' becomes 'cur' (a cur is an aggressive or scruffy dog).
'with' is a charade indicator (letters next to each other).
'a trouble' becomes 'ail' (I've seen this before).
'free' is a deletion indicator (the word is freed of certain letters).
'tail' with 'ail' taken away is 't'.
'cur'+'t'='CURT'
Can you help me to learn more?
(Other definitions for curt that I've seen before include "Brief and terse" , "Rudely blunt" , "Dismissively short" , "Rudely brief" , "Concise" .)