Helen, Pat, Rocky and Jumbo (8)
I believe the answer is:
elephant
'jumbo' is the definition.
(thesaurus)
'helen pat rocky' is the wordplay.
'rocky' indicates anagramming the letters.
'helen'+'pat'='helenpat'
'helenpat' is an anagram of 'ELEPHANT'.
'and' is the link.
(Other definitions for elephant that I've seen before include "Huge mammal" , "Large animal found in the plane?" , "bigger one from two continents?" , "Trunked mammal" , "Huge African or Indian animal" .)