Spent almost a hundred on queen's garment (7)
I believe the answer is:
spencer
'garment' is the definition.
(I've seen this before)
'spent almost a hundred on queen's' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'a hundred' becomes 'C' (Roman numeral).
'on' means one lot of letters go next to another.
'queen' becomes 'ER' (abbreviation for Elizabeth Regina).
'spent' with its last letter taken away is 'spen'.
'spen'+'c'+'er'='SPENCER'
(Other definitions for spencer that I've seen before include "Garment" , "Churchill's name" , "Short jacket" , "An academician" , "A woman's knitted vest" .)