Nixon, not on course, sadly making deviation (9)
I believe the answer is:
excursion
'deviation' is the definition.
(thesaurus)
'nixon not on course sadly' is the wordplay.
'not' suggests deleting specific letters.
'sadly' indicates anagramming the letters.
'nixon' with 'on' taken out is 'nix'.
'nix'+'course'='nixcourse'
'nixcourse' anagrammed gives 'EXCURSION'.
'making' is the link.
(Other definitions for excursion that I've seen before include "Jaunt" , "Insure cox on pleasure trip" , "Pleasure outing" , "Day-trip" , "Outing, junket" .)