Formerly restricted to nine tons after gamble with weight (7)
I believe the answer is:
betwixt
'formerly restricted to' is the definition.
I can't judge whether this defines the answer.
'nine tons after gamble with weight' is the wordplay.
'nine' becomes 'IX' (roman numeral).
'tons' becomes 't'.
'after' says to put letters next to each other.
'gamble' becomes 'bet' (betting is a kind of gambling).
'with weight' becomes 'w' (short for weight. I am not sure about the 'with' bit.).
'ix'+'t'='ixt'
'bet'+'w'='betw'
'ixt' put after 'betw' is 'BETWIXT'.
Can you help me to learn more?
(Other definitions for betwixt that I've seen before include "In the middle of" , "Between (arch.)" , "Old word for between" .)