A survey has nothing on a Greek god (6)
I believe the answer is:
apollo
'a greek god' is the definition.
(Apollo is an example)
'a survey has nothing' is the wordplay.
'survey' becomes 'poll' (polling is a kind of surveying).
'has' means one lot of letters go next to another.
'nothing' becomes 'O' (looks like zero - 0).
'a'+'poll'+'o'='APOLLO'
'on' acts as a link.
(Other definitions for apollo that I've seen before include "Programme targeting satellite" , "Greek god of the sun (6)" , "Greek (and Roman) god of light, poetry etc" , "US moon landing programme" , "US spacecraft" .)