Small amount of water, perhaps, that's found in a kettle (7)
I believe the answer is:
element
I believe this is a triple definition!
'small amount' is the first definition.
(I've seen this before)
'of' is a link.
'water perhaps' is the second definition.
(water is a kind of element)
'that's found in a kettle' is the third definition.
(heating element)
(Other definitions for element that I've seen before include "Basic substance or feature" , "Essential factor" , "briefly identified by Al or Mo, among others" , "Basic chemical unit" , "lead, for example" .)