Problem raised about outfield isn't surprising, given this many errors? (9,2,4)

'this many errors?' is the definition.
The definition suggests a singular noun which matches the answer.

'problem raised about outfield isn't surprising' is the wordplay.
'problem' becomes 'sum' (arithmetic problem**).
'raised' says the letters should be written in reverse.
'about' is an insertion indicator.
'surprising' indicates anagramming the letters.
'sum' in reverse letter order is 'mus'.
'outfield'+'isnt'='outfieldisnt'
'outfieldisnt' with letters rearranged gives 'ltitudeofsin'.
'mus' enclosing 'ltitudeofsin' is 'MULTITUDE OF SINS'.

'given' acts as a link.