Helmsman making variant go wrong (9)
I believe the answer is:
navigator
'helmsman' is the definition.
(thesaurus)
'variant go wrong' is the wordplay.
'wrong' indicates an anagram.
'variant'+'go'='variantgo'
'variantgo' anagrammed gives 'NAVIGATOR'.
'making' acts as a link.
(Other definitions for navigator that I've seen before include "One who plots a course" , "Prince Henry, say" , "For example, Henry" , "One directs the course, of a ship say" , "Marine explorer" .)