Boring lead tenors anger a few backers (8)
I believe the answer is:
tiresome
'boring' is the definition.
(I know that boring can be written as tiresome)
'lead tenors anger a few backers' is the wordplay.
I cannot quite see how this works, but
'anger' could be 'ire' (ire is intense rage) and 'ire' is found within the answer.
'few' could be 'some' (associated in meaning) and 'some' is located in the answer.
A single letter 't' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tiresome that I've seen before include "'Tedious, irksome (8)'" , "Wearying" , "Causing boredom" , "Aggravating" , "wearing" .)