Topless brothel-keeper expelled gardener (4)
I believe the answer is:
adam
'expelled gardener' is the definition.
(I've seen this before)
'topless brothel-keeper' is the wordplay.
'topless' means to remove the first letter.
'brothel keeper' becomes 'madam' (synonyms).
'madam' with its first letter taken off is 'ADAM'.
(Other definitions for adam that I've seen before include "__ Smith, author of The Wealth of Nations" , "Biblical first man" , "First Christian ancestor" , "Robert-, eighteenth century Scots architect" , "Early man" .)