In favour of going up to the far end (3)
I believe the answer is:
for
'in favour' is the definition.
(I've seen this before)
'of going up to the far end' is the wordplay.
'going up' says the letters should be written backwards.
'to' says to put letters next to each other.
'end' indicates one should take the final letters.
The final letter of 'far' is 'r'.
'of' written backwards gives 'fo'.
'fo'+'r'='FOR'
(Other definitions for for that I've seen before include "On behalf of" , "In support of" , "See 24" , "Approving" , "Favouring" .)