Toilet drops its third rental sign (2,3)
I believe the answer is:
to let
'rental sign' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for to let that I've seen before include "Available for a tenant" , "Available for renting" , "open to offers" , "Estate agent's sign" , "Sign of the property market" .)