Bag carried by pensioners at Chelsea (7)
I believe the answer is:
satchel
'bag' is the definition.
(I've seen this before)
'carried by pensioners at chelsea' is the wordplay.
'carried by' says the answer is hidden in the clue.
'SATCHEL' can be found hidden inside 'pensioners at chelsea'.
(Other definitions for satchel that I've seen before include "Schoolbag found in chalets" , "Bag with a flap and strap" , "Small case with a shoulder strap" , "Carrier for school books" , "What's carried by pupils" .)