High-tech step taken by government advisory body (5-3)
I believe the answer is:
space-age
'high-tech' is the definition.
'step taken by government advisory body' is the wordplay.
'step' becomes 'pace' (synonyms).
'taken by' means one lot of letters goes inside another.
'government advisory body' becomes 'sage' (Scientific Advisory Group for Emergencies).
'pace' put within 'sage' is 'SPACE-AGE'.
(Other definitions for space-age that I've seen before include "Futuristic" , "Ultra-modern" .)