Confess, accepting case of perjury -- it's intelligence work (6)
I believe the answer is:
Here is my best explanation:
'intelligence work' is the definition.
'confess accepting case of perjury' is the wordplay.
'confess' becomes 'sing' (I've seen this before).
'accepting' means one lot of letters goes inside another.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'perjury' with its centre taken out is 'py'.
'sing' placed around 'py' is 'SPYING'.
'it's' is the link.