Old canine barking on time (7)
I believe the answer is:
ancient
'old' is the definition.
(similar in meaning)
'canine barking on time' is the wordplay.
'barking' is an anagram indicator (UK slang for mad).
'on' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'canine' with letters rearranged gives 'ancien'.
'ancien'+'t'='ANCIENT'
(Other definitions for ancient that I've seen before include "Historic standard" , "from Aristophanes' time" , "over the hill" , "Pistol" , "Extremely old" .)