One more convert on earth (7)
I believe the answer is:
another
'one more' is the definition.
(I've seen this before)
'convert on earth' is the wordplay.
'convert' indicates an anagram (I've seen this in other clues).
'on'+'earth'='onearth'
'onearth' with letters rearranged gives 'ANOTHER'.
(Other definitions for another that I've seen before include "Additional, one more" , "A different (thing)" , "Someone else" , "second" , "Somebody else" .)