Bag locks by flipping sides (7)
I believe the answer is:
satchel
'bag' is the definition.
(I've seen this before)
'locks by flipping sides' is the wordplay.
I cannot really see how this works, but
'by' could be 'at' and 'at' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for satchel that I've seen before include "Small case with a shoulder strap" , "Schoolbag found in chalets" , "Get school item" , "Schoolchild's carrier" , "Text mark for an insertion" .)