Reptile displays pride in Tarsus recklessly (9)
I believe the answer is:
stegosaur
'reptile' is the definition.
(stegosaur is a kind of reptile)
'pride in tarsus recklessly' is the wordplay.
'pride' becomes 'ego' (ego is a kind of pride).
'in' indicates putting letters inside.
'recklessly' indicates an anagram.
'tarsus' anagrammed gives 'stsaur'.
'ego' going into 'stsaur' is 'STEGOSAUR'.
'displays' is the link.
(Other definitions for stegosaur that I've seen before include "Old beast" , "Jurassic creature" , "Old veggie" , "old dinosaur" , "Armoured fossil creature" .)