Start and finish not clearly defined (4-3)

I believe the answer is:

open-end

'not clearly defined' is the definition.
(open-end can mean lacking a clear boundary)

'start and finish' is the wordplay.
'start' becomes 'open' (opening is a kind of starting).
'and' means one lot of letters go next to another.
'finish' becomes 'end' (synonyms).
'open'+'end'='OPEN-END'

(Another definition for open-end that I've seen is " not closely defined".)

I've seen this clue in The Times.

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