Bag hidden in flowers at Chelsea (7)
I believe the answer is:
satchel
'bag' is the definition.
(I know that satchel is a type of bag)
'hidden in flowers at chelsea' is the wordplay.
'hidden in' says the answer is hidden in the clue.
'SATCHEL' is hidden within 'flowers at chelsea'.
(Other definitions for satchel that I've seen before include "Carrier for school books" , "Bag with a flap and strap" , "Bag -- latches (anag)" , "What's carried by pupils" , "Shoulder bag as for schoolbooks" .)