Daughter spilled petrol, the tiniest amount (7)
I believe the answer is:
droplet
'tiniest amount' is the definition.
'droplet' can be an answer for 'amount' (droplet is a kind of amount). I'm not certain of the 'tiniest' bit.
'daughter spilled petrol' is the wordplay.
'daughter' becomes 'd' (genealogical abbreviation).
'spilled' indicates an anagram.
'petrol' with letters rearranged gives 'roplet'.
'd'+'roplet'='DROPLET'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for droplet that I've seen before include "Small globule" , "Small blob of liquid" , "Small amount of liquid" , "Tiny bead of liquid" , "Small quantity of water, as in cloud" .)