Warcraft from America's leader, but so refined (1-5)
I believe the answer is:
u-boats
'warcraft' is the definition.
'america's leader but so refined' is the wordplay.
'leader' says to take the initial letters.
'refined' is an anagram indicator.
The first letter of 'americas' is 'a'.
'a'+'but'+'so'='abutso'
'abutso' with letters rearranged gives 'U-BOATS'.
'from' is the link.
(Other definitions for u-boats that I've seen before include "German submarines of second World War" , "Submersible warships" , "Submersible ships of WW2" , "German subs" , "German submarines in WW2" .)