Suggestions one thousand are involved in revolutionary swindles (6)
I believe the answer is:
'suggestions' is the definition.
(smack can mean a suggestion or trace of something)
'one thousand are involved in revolutionary swindles' is the wordplay.
'one thousand' becomes 'K' (synonyms).
'are involved in' means one lot of letters goes inside another.
'revolutionary' shows that the letters should be reversed in order (letters revolve around).
'swindles' becomes 'scams' (scam is a kind of swindle).
'scams' in reverse letter order is 'smacs'.
'k' inserted within 'smacs' is 'SMACKS'.
(Other definitions for smacks that I've seen before include "Fishing ships with sails" , "Punishes" , "Slaps; flavours; boats" , "Boxes" , "Horse's" .)