Grows weary (5)
'grows weary' is the definition.
('tire' can be a synonym of 'grow weary')
This is the entire clue.
(Other definitions for tires that I've seen before include "Weakens" , "Grows weary of rites" , "Becomes weary and in need of rest" , "Exhausts" , "Wearies" .)
(Other definitions for flags that I've seen before include "Grows languid" , "Paving stones" , "Tires; national symbols" , "Banners" , "Standards" .)