Wet on the day, thought the water isn't settling (8)

'isn't settling' is the definition.
The definition and answer can be both related to change as well as being present participle verbs.
Maybe there's an association between them I don't understand?

'wet on the day thought the water' is the wordplay.
'wet' becomes 'rain' (wet weather).
'on' says to put letters next to each other.
'the day' becomes 'd' (abbreviation for day).
'thought the water' becomes 'ing' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rain' after 'd' is 'drain'.
'drain'+'ing'='DRAINING'

Can you help me to learn more?