Oscar's on edge but not very tiresome (7)
I believe the answer is:
onerous
'tiresome' is the definition.
(thesaurus)
'oscar's on edge but not very' is the wordplay.
'oscar's' becomes 'o' (this might be a standard abbreviation I've not previously seen).
'on edge' becomes 'nervous' (I've seen this in another clue).
'but not' indicates named letters should be taken away.
'very' becomes 'v' (common abbreviation).
'nervous' with 'v' removed is 'nerous'.
'o'+'nerous'='ONEROUS'
Can you help me to learn more?
(Other definitions for onerous that I've seen before include "Oppressive, difficult to bear" , "Burdensome, taxing" , "Burdensome, heavy kind of duty" , "weight" , "quite a burden if so" .)