Informs students in set up (5)
I believe the answer is:
tells
'informs' is the definition.
(telling is a kind of informing)
'students in set up' is the wordplay.
'students' becomes 'LL' (two abbreviations for learner).
'in' means one lot of letters goes inside another.
'up' is a reversal indicator (in down clue: letters go upwards).
'll' inserted within 'set' is 'sllet'.
'sllet' reversed gives 'TELLS'.
(Other definitions for tells that I've seen before include "Informs, recounts" , "Counts" , "Narrates" .)