About to interrupt low-down politician (5)
I believe the answer is:
green
'politician' is the definition.
(eg member of the Green Party)
'about to interrupt low-down' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to interrupt' means one lot of letters goes inside another.
'low down' becomes 'gen' (both can mean information).
're' going inside 'gen' is 'GREEN'.
(Other definitions for green that I've seen before include "Gullible" , "Politician perhaps" , "Flourishing" , "Envious -- environmentalist" , "Raw - inexperienced" .)