Confuse intelligence about National Physical Laboratory (7)
I believe the answer is:
nonplus
'confuse' is the definition.
(I know that nonplus is a more specific form of the action confuse)
'intelligence about national physical laboratory' is the wordplay.
'intelligence' becomes 'nous' (I've seen this before).
'about' is an insertion indicator.
'national physical laboratory' becomes 'NPL' (abbreviation).
'nous' going around 'npl' is 'NONPLUS'.
(Other definitions for nonplus that I've seen before include "Perplex, confound" , "Baffle" , "Throw into confusion" , "Put at a loss; confuse" , "Surprise and confuse" .)