Set goals every lesson, initially (3)
I believe the answer is:
gel
'set' is the definition.
(both can mean to harden)
'goals every lesson initially' is the wordplay.
'initially' indicates taking the first letters.
The initial letters of 'goals every lesson' is 'GEL'.
(Other definitions for gel that I've seen before include "Thicken" , "shock treatment" , "It may be applied to locks" , "Come together, take shape (colloq.)" , "Begin to work" .)