To the Poles, a substantial amount (4)
I believe the answer is:
tons
'a substantial amount' is the definition.
'tons' can be an answer for 'amount' (tons is a kind of amount). I'm unsure of the 'a substantial' bit.
'to the poles' is the wordplay.
'the poles' becomes 'ns' (north and south poles).
'to'+'ns'='TONS'
Can you help me to learn more?
(Other definitions for tons that I've seen before include "Loads (sl.)" , "Each is equivalent to 2240 pounds" , "A lot" , "Lots" .)