A few entries onscreen and financier finally invested in essential fuels (10)

'a few entries onscreen' is the definition.
I don't know anything about this answer so I can't tell whether this works.

'financier finally invested in essential fuels' is the wordplay.
'finally' indicates one should take the final letters.
'invested in' is an insertion indicator.
'essential' becomes 'key' (I've seen this before).
'fuels' becomes 'stokes' (I can't explain this - if you can you should give a lot more credence to this answer).
The last letter of 'financier' is 'r'.
'key'+'stokes'='keystokes'
'r' inserted into 'keystokes' is 'KEYSTROKES'.

'and' acts as a link.

Can you help me to learn more?