Rain-affected sash generates capital (7)
I believe the answer is:
nairobi
'capital' is the definition.
(capital of Kenya)
'rain-affected sash' is the wordplay.
'affected' is an anagram indicator.
'sash' becomes 'obi' (type of Japanese sash or belt).
'rain' anagrammed gives 'nair'.
'nair'+'obi'='NAIROBI'
'generates' is the link.
(Other definitions for nairobi that I've seen before include "The capital of Kenya (7)" , "I, a robin (anag) - city" , "East African capital" , "City of Kenya" , "African city" .)