Within enclosed chamber, metres inside, tie down stateside digging equipment (9)
I believe the answer is:
clamshell
'stateside digging equipment' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'within enclosed chamber metres inside tie down' is the wordplay.
'within' is an insertion indicator.
'enclosed chamber' becomes 'cell' (I've seen this before. I am not sure about the 'enclosed' bit.).
'metres' becomes 'm'.
'inside' is an insertion indicator.
'tie down' becomes 'lash' (I've seen this in another clue).
'm' going into 'lash' is 'lamsh'.
'cell' going around 'lamsh' is 'CLAMSHELL'.
Can you help me to learn more?
(Another definition for clamshell that I've seen is " perhaps for a fast food box?".)