£1,000 initially spent on young relative (8)
I believe the answer is:
grandson
'young relative' is the definition.
'grandson' can be an answer for 'relative' (grandson is a type of relative). I'm unsure of the 'young' bit.
'ps1000 initially spent on' is the wordplay.
'psg000' becomes 'grand' (I am not sure about this - if you are sure you should believe this answer much more).
'initially' indicates taking the first letters.
The initial letter of 'spent' is 's'.
'grand'+'s'+'on'='GRANDSON'
Can you help me to learn more?
(Other definitions for grandson that I've seen before include "Male descendent" , "Male child of one's child" , "Junior relative" , "Young male relative" , "Younger male relative" .)