Flower given by old cheat going round in South American city (7)
I believe the answer is:
orinoco
'flower' is the definition.
(Orinoco River is an example)
'old cheat going round in south american city' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'cheat' becomes 'con' (con is a kind of cheat).
'going round' says the letters should be written backwards.
'in' means one lot of letters goes inside another.
'south american city' becomes 'rio' (I've seen this in other clues).
'con' in reverse letter order is 'noc'.
'noc' inserted within 'rio' is 'rinoco'.
'o'+'rinoco'='ORINOCO'
'given by' acts as a link.
(Other definitions for orinoco that I've seen before include "moves between South American banks" , "resident on Wimbledon Common" , "Womble; S. Amer. river" , "may be seen running through South America" , "South American river flowing into the Atlantic" .)