Some pretend lesson gets monotonous (7)
I believe the answer is:
endless
'monotonous' is the definition.
(thesaurus)
'some pretend lesson gets' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ENDLESS' is hidden within 'pretend lesson gets'.
(Other definitions for endless that I've seen before include "Sister of Aaron (Exodus)" , "Going on forever, lacking conclusion" , "Unceasing" , "Going on and on, interminable" , "Continuous - eternal - incessant" .)