Old and loose canine out at last (7)
I believe the answer is:
ancient
'old' is the definition.
('ancient' can be similar in meaning to 'old')
'loose canine out at last' is the wordplay.
'loose' indicates anagramming the letters (letters are loosened from their original positions).
'at last' says to take the final letters.
The final letter of 'out' is 't'.
'canine' anagrammed gives 'ancien'.
'ancien'+'t'='ANCIENT'
'and' is the link.
(Other definitions for ancient that I've seen before include "Shakespearean standard-bearer" , "from Aristophanes' time" , "Very old, belonging to times long ago" , "Archaic" , "of long standing" .)