Unlikely a rich crossword setter's included - that's fantasy (7)
I believe the answer is:
chimera
'fantasy' is the definition.
(I've seen this before)
'unlikely a rich crossword setter's included' is the wordplay.
'unlikely' indicates an anagram (an unlikely spelling of the letters).
'crossword setter' becomes 'me' (referring to the person writing the clues).
'included' means one lot of letters goes inside another.
'a'+'rich'='arich'
'arich' is an anagram of 'chira'.
'chira' placed around 'me' is 'CHIMERA'.
'that's' is the link.
(Other definitions for chimera that I've seen before include "Wild or impossible idea" , "Lion-headed monster" , "In Greek myth, a monster-mix of lion, goat and serpent" , "Illusory goal; monster" , "Mythical creature; delusion" .)