A large one gets foremost of topers settled (4)
I believe the answer is:
alit
'settled' is the definition.
(I've seen this before)
'a large one gets foremost of topers' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'one' becomes 'i' (Roman numeral).
'gets' means one lot of letters go next to another.
'foremost of' indicates taking the first letters.
The first letter of 'topers' is 't'.
'a'+'l'+'i'+'t'='ALIT'
(Other definitions for alit that I've seen before include "Came down to earth" , "got off" , "Settled" , "Climbed down from" , "Landed" .)