A gene mutation follows a location for Rhodes (6)
I believe the answer is:
aegean
'location for rhodes' is the definition.
(I know that Rhodes location Aegean)
'a gene mutation follows a' is the wordplay.
'mutation' indicates anagramming the letters.
'follows' is a charade indicator (letters next to each other).
'a'+'gene'='agene'
'agene' with letters rearranged gives 'egean'.
'egean' after 'a' is 'AEGEAN'.
(Other definitions for aegean that I've seen before include "Sea, an arm of the Mediterranean" , "Sea between Greece/Turkey" , "Sea bordering 20 ac" , "area of sea" , "Greek sea" .)