Flower shirts (4)
I believe the answer is:
tees
This clue is a double definition.
'flower' is the first definition.
(River Tees)
'shirts' is the second definition.
(T-shirts)
(Other definitions for tees that I've seen before include "River on which Middlesbrough stands" , "sand-hills" , "Golf pegs" , "River of north-east England" , "Durham's river" .)