Spied for heads of national organisation, scrutinising every document (5)
I believe the answer is:
nosed
'spied' is the definition.
'heads of national organisation scrutinising every document' is the wordplay.
'heads of' suggests taking the first letters.
The first letters of 'national organisation scrutinising every document' is 'NOSED'.
'for' acts as a link.
(Other definitions for nosed that I've seen before include "proceeded gingerly" , "Nodes (anag.)" , "Move back or away" , "smelt" , "proceeded slowly" .)