Well-worn section of trail I'm afterwards to climb (8)
I believe the answer is:
familiar
'well-worn' is the definition.
(thesaurus)
'section of trail i'm afterwards to climb' is the wordplay.
'section of' indicates the answer is hidden within the clue.
'to climb' says the letters should be written backwards (I've seen 'climbs' mean this).
'railimaf' can be found hidden inside 'trail im afterwards'.
'railimaf' in reverse letter order is 'FAMILIAR'.
(Other definitions for familiar that I've seen before include "routine" , "Witch's cat is well acquainted" , "Well known or easily recognised" , "spirit" , "Conservant with the witch's cat?" .)