Aid learner, one cutting the knot? (6)
I believe the answer is:
relief
'aid' is the definition.
(relief is a kind of aid)
'learner one cutting the knot?' is the wordplay.
'learner' becomes 'l'.
'one' becomes 'I' (Roman numeral).
'cutting' means one lot of letters goes inside another (some letters cut their way into a word).
'the knot?' becomes 'reef' (reef knot is a kind of knot).
'l'+'i'='li'
'li' placed inside 'reef' is 'RELIEF'.
(Other definitions for relief that I've seen before include "Person taking over another's turn of duty" , "Ease from pain" , "A lightening of pressure" , "Assistance given to people in need" , "Lightening of oppression" .)