City custom mainly associated with a sprout (3,5)
I believe the answer is:
abu dhabi
'city' is the definition.
(Abu Dhabi is an example)
'custom mainly associated with a sprout' is the wordplay.
'custom' becomes 'habit' (habit is a kind of custom).
'mainly' means to remove the last letter.
'associated with' means one lot of letters go next to another.
'sprout' becomes 'bud' (bud is a kind of sprout).
'habit' with its last letter taken off is 'habi'.
'a'+'bud'='abud'
'habi' put after 'abud' is 'ABU DHABI'.
(Other definitions for abu dhabi that I've seen before include "Part of UAE" , "Persian Gulf emirate" , "Largest member state of the UAE, and its capital" , "Federal capital of the United Arab Emirates" , "foreign land" .)