Locus for enthusiasts regularly using revolutionary toy (7)
I believe the answer is:
meccano
'toy' is the definition.
(I know that Meccano is a type of toy)
'locus for enthusiasts regularly using revolutionary' is the wordplay.
'locus for enthusiasts' becomes 'mecca' (Mecca can informally mean a place for enthusiasts).
'regularly using' becomes 'on' (on drugs).
'revolutionary' is a reversal indicator (letters revolve around).
'on' back-to-front is 'no'.
'mecca'+'no'='MECCANO'
(Other definitions for meccano that I've seen before include "constructive materials" , "Metal model construction set" , "It's for kids' building" , "Building material" , "Plaything" .)