Put down help needed by learner (4)
I believe the answer is:
laid
'put down' is the definition.
(to lay something is to put it down somewhere)
'help needed by learner' is the wordplay.
'help' becomes 'aid' (synonyms).
'needed by' is a charade indicator (letters next to each other).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'aid' after 'l' is 'LAID'.
(Other definitions for laid that I've seen before include "Placed horizontally on a surface" , "Prepared (a trap)" , "spread on a surface" , "Deposited" , "settled" .)