A tailless dog causes a commotion (3)
I believe the answer is:
ado
'a commotion' is the definition.
(ado is a kind of commotion)
'a tailless dog' is the wordplay.
'tailless' means to remove the last letter (the tail of the word is removed).
'dog' with its last letter taken away is 'do'.
'a'+'do'='ADO'
'causes' acts as a link.
(Other definitions for ado that I've seen before include "Flurry" , "Flap" , "stir" , "Rapid bustling commotion" , "puff ball!" .)