Theatre taking up a lot of time? (5)
I believe the answer is:
arena
'theatre' is the definition.
(I've seen this before)
'up a lot of time?' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'a' becomes 'an'.
'lot' means to remove the last letter (I've seen 'lots of' mean this (the majority of the word)).
'of time?' becomes 'eral' (I've seen this in another clue).
'eral' with its final letter taken off is 'era'.
'an'+'era'='anera'
'anera' back-to-front is 'ARENA'.
'taking' is the link.
(Other definitions for arena that I've seen before include "Sporting venue enclosed by seats" , "where there's competition" , "Place of public contest" , "Area of endeavour" , "dramatic situation" .)