Buying and selling clubs provided Trump with turnover (7)
I believe the answer is:
traffic
'buying and selling' is the definition.
(I've seen this in another clue)
'clubs provided trump with turnover' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'trump with' becomes 'fart' (both can mean flatulence. I am not sure about the 'with' bit.).
'turnover' says the letters should be written in reverse (the letters turn over).
'c'+'if'+'fart'='ciffart'
'ciffart' in reverse letter order is 'TRAFFIC'.
Can you help me to learn more?
(Other definitions for traffic that I've seen before include "Communications" , "Trade (in cars?)" , "Truck" , "Deal illegally , in drugs say" , "Sort of light" .)