Jets start out from them (13)

I believe the answer is:

fountainheads

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'them' is the definition.
I can't judge whether this defines the answer.

'jets start out from' is the wordplay.
'jets' becomes 'fountains' ('fountain' can be a synonym of 'jet').
'start' means to remove the last letter (I've seen 'starts' mean this).
'out from' becomes 'heads' (I can't justify this - if you can you should give a lot more credence to this answer).
'fountains' with its final letter taken away is 'fountain'.
'fountain'+'heads'='FOUNTAINHEADS'

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I've seen this clue in The Globe and Mail.

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