Elaine occasionally in position on course (3)
I believe the answer is:
lie
'position on course' is the definition.
'lie' can be an answer for 'course' (thesaurus). I am not sure about the 'position on' bit.
'elaine occasionally' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternating letters of 'elaine' are 'LIE'.
'in' is the link.
Can you help me to learn more?
(Other definitions for lie that I've seen before include "Disinformation" , "Be prone - misrepresent the facts" , "Prevarication" , "Stay hidden" , "Fib - be prone" .)