Talk and pant, no end (3)
I believe the answer is:
gas
'talk' is the definition.
(thesaurus)
'pant no end' is the wordplay.
'pant' becomes 'gasp' ('gasp' can be a synonym of 'pant').
'no end' means to remove the last letter.
'gasp' with its last letter removed is 'GAS'.
'and' is the link.
(Other definitions for gas that I've seen before include "natural resource" , "Piped fuel" , "Talk idly; fuel" , "Petrol (US)" , "Talk excessively" .)