Study is set up — that is to finish some time or other (4,3)
I believe the answer is:
sine die
'some time or other' is the definition.
(Latin phrase meaning with no appointed date)
'study is set up that is to finish' is the wordplay.
'study' becomes 'den' (term for a study or office).
'set up' is a reversal indicator (in a down clue, letters go up).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'to finish' means one lot of letters go next to another (some letters go after or 'finish' others).
'den'+'is'='denis'
'denis' reversed gives 'sined'.
'sined'+'ie'='SINE DIE'
(Other definitions for sine die that I've seen before include "For an indefinite period (Latin)" , "indefinitely adjourned" , "With no appointed date for resumption (Latin)" , "With no date set for resumption (Latin)" , "undated" .)