Worked endlessly needing time for facilities (6)
I believe the answer is:
toilet
'facilities' is the definition.
(thesaurus)
'worked endlessly needing time' is the wordplay.
'worked' becomes 'toiled' (toiling is a kind of working).
'endlessly' means to remove the last letter.
'needing time' becomes 't' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'toiled' with its last letter taken off is 'toile'.
'toile'+'t'='TOILET'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for toilet that I've seen before include "Smallest room" , "WC" , "Lavatory paper" , "something to go on?" , "It means washing" .)