Mammoth and moose run awkwardly (8)
I believe the answer is:
enormous
'mammoth' is the definition.
(synonyms)
'moose run awkwardly' is the wordplay.
'awkwardly' indicates an anagram.
'moose'+'run'='mooserun'
'mooserun' is an anagram of 'ENORMOUS'.
'and' is the link.
(Other definitions for enormous that I've seen before include "Mammoth" , "Unusually large - jumbo" , "Huge, really big" , "Immense" , "Vast" .)