Old description of Smilodon! (4,2,3,5)
I believe the answer is:
long in the tooth
'old' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for long in the tooth that I've seen before include "Was a woolly mammoth" , "ancient?" , "aged" , "indication of the need for cosmetic dentistry?" , "like smilodon?" .)