Pounds mistakenly paid for being boring (5)
I believe the answer is:
vapid
'being boring' is the definition.
(I've seen this before)
'pounds mistakenly paid' is the wordplay.
I cannot really understand how this works, but
an anagram of 'paid' is 'apid' which is present in the answer.
A single letter 'v' 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).
'for' acts as a link.
Can you help me to learn more?
(Other definitions for vapid that I've seen before include "Boring, flat" , "Wishy-washy" , "Offering no stimulation" , "Boring or lifeless" , "Dull, insipid, flat" .)