Prompt to welcome learner’s hint (4)
I believe the answer is:
clue
'hint' is the definition.
(I know that hint can be written as clue)
'prompt to welcome learner's' is the wordplay.
'prompt' becomes 'cue' (cue can mean a prompt or signal).
'to welcome' indicates putting letters inside (in sense of 'inviting in').
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'cue' going around 'l' is 'CLUE'.
(Other definitions for clue that I've seen before include "Hint to help the puzzler" , "Crossword item" , "Crossword help" , "Slight indication (as here)" , "One of twenty-four in this puzzle" .)