To term clerics eccentric creates great disturbance (8,5)
I believe the answer is:
electric storm
'great disturbance' is the definition.
(disturbance of the atmosphere)
'to term clerics eccentric' is the wordplay.
'eccentric' indicates an anagram.
'to'+'term'+'clerics'='totermclerics'
'totermclerics' is an anagram of 'ELECTRIC STORM'.
'creates' is the link.
(Other definitions for electric storm that I've seen before include "Violent atmospheric disturbance" , "A highly charged disturbance?" , "creates a great disturbance" .)