Inexperienced regarding blocking information (5)
I believe the answer is:
Here is my best explanation:
'inexperienced' is the definition.
('green' can be similar in meaning to 'inexperienced')
'regarding blocking information' is the subsidiary indication.
'regarding' becomes 're'.
'blocking' is an insertion indicator.
'information' becomes 'gen' (gen is a kind of information**).
're' put within 'gen' is 'green'.
(Other definitions for green that I've seen before include "Politician; fresh", "The colour of immaturity", "Raw - inexperienced", "bowlers here?", "conservationist", "It's for putting on - colour - inexperienced", "Permission to proceed", "Environmentally sound", "Putting area" and "Ecologically sound".)