Fraudulent scheme placing restraint on tenant (5,6)
I believe the answer is:
chain letter
'fraudulent scheme' is the definition.
(I've seen this before)
'restraint on tenant' is the wordplay.
'restraint' becomes 'chain' (chain is a kind of restraint).
'on' means one lot of letters go next to another.
'tenant' becomes 'letter' (someone who lets a property).
'chain'+'letter'='CHAIN-LETTER'
'placing' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
(Other definitions for chain letter that I've seen before include "Fast-spreading communication" , "Sequential correspondence" , "The clarinet (anag.)" , "one sent mushrooming?" , "Cascading correspondence" .)