Number regularly found in Indian tea (4)
I believe the answer is:
nine
'number' is the definition.
(nine is a kind of number)
'regularly found in indian tea' is the wordplay.
'regularly found in' means one should take alternating letters.
'indian'+'tea'='indiantea'
The alternating letters of 'indiantea' are 'NINE'.
(Other definitions for nine that I've seen before include "Number for a club" , "One over the eight" , "Days Lady Jane 5 ac reigned" , "One more than fourteen across" , "Square next up after four" .)