Green’s Dictionary of Slang

one who assists in the eviction of tenants, usu. by means of threats and pressure.

1970		Sun. Times 15 Nov. 3/5: Plausible, highly-paid ‘winklers’ who are hired by property companies and landlords to persuade families to leave their rent-controlled tenancies so the homes can be sold at high prices.
1977		Whig-Standard (Kingston, Ontario) 29 Sept. 26/3: The tenants said the agents aided by middlemen called ‘winklers’, had bribed and harassed them to get them to move [OED].