Fell on taxpayers to sort out -- that's obvious (4-11)

I believe the answer is:

self-explanatory

'obvious' is the definition.
(I've seen this before)

'fell on taxpayers to sort out' is the wordplay.
'to sort out' indicates anagramming the letters.
'fell'+'on'+'taxpayers'='fellontaxpayers'
'fellontaxpayers' is an anagram of 'SELF-EXPLANATORY'.

'that's' is the link.

(Another definition for self-explanatory that I've seen is " Not needing any introduction".)

I've seen this clue in The Telegraph.

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