Closure of zoo interrupting bear's routine (6)
I believe the answer is:
boring
'routine' is the definition.
(routine can mean familiar or boring)
'closure of zoo interrupting bear's' is the wordplay.
'closure of' indicates one should take the final letters.
'interrupting' is an insertion indicator.
'bear' becomes 'bring' (both can mean to carry).
The last letter of 'zoo' is 'o'.
'o' going within 'bring' is 'BORING'.
(Other definitions for boring that I've seen before include "Drilling - it's monotonous" , "Dull and repetitive, a turn-off" , "Drilling can be tedious" , "Tedious, tiresome" , "Tedious and tiring" .)