On Earth evolution is different (7)
I believe the answer is:
another
'different' is the definition.
(synonyms)
'on earth evolution' is the wordplay.
'evolution' is an anagram indicator.
'on'+'earth'='onearth'
'onearth' with letters rearranged gives 'ANOTHER'.
'is' is the link.
(Other definitions for another that I've seen before include "No heart (anag.)" , "A further (item)" , "Player or person not yet named or selected" , "Additional: alternative" , "A different (thing)" .)