Spend lots of money installing switch in jet (6,3)
I believe the answer is:
splash out
'spend lots' is the definition.
I can't tell whether this definition defines the answer.
'money installing switch in jet' is the wordplay.
'money' becomes 'l' (L can mean 'pounds').
'installing switch' becomes 'ash' (I can't explain this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'jet' becomes 'spout' (I have seen 'Jet of liquid' mean 'spout' so perhaps 'jet' could also mean 'spout').
'l'+'ash'='lash'
'lash' put within 'spout' is 'SPLASH OUT'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for splash out that I've seen before include "Spend money freely" , "Spend a lot of money" , "Blow brass" , "extravagant" .)