Around start of lesson I spell 'curlicue' (5)
I believe the answer is:
helix
'curlicue' is the definition.
(thesaurus)
'around start of lesson i spell' is the wordplay.
'around' means one lot of letters goes inside another.
'start of' says to take the initial letters.
'spell' becomes 'hex' (hex is a kind of spell**).
The initial letter of 'lesson' is 'l'.
'l'+'i'='li'
'li' put inside 'hex' is 'HELIX'.
(Other definitions for helix that I've seen before include "Spiral (maybe double)" , "Screwed coil" , "Three-dimensional object shaped like a corkscrew" , "Structure made up of a continuous series of loops" , "Object with a three-dimensional shape, like a corkscrew" .)