Ground water covering street beside lake beginning to drain (7)

'ground water' is the definition.
'pestled' can be an answer for 'ground' (pestling is a kind of grinding). I'm unsure of the 'water' bit.

'covering street beside lake beginning to drain' is the wordplay.
'covering' means one lot of letters goes inside another.
'street' becomes 'st' (abbreviation).
'beside' says to put letters next to each other (I've seen this in other clues).
'beginning to' suggests taking the first letters.
'drain' becomes 'peed' (I can't explain this - if you can you should give a lot more credence to this answer).
The first letter of 'lake' is 'l'.
'st'+'l'='stl'
'stl' placed into 'peed' is 'PESTLED'.

Can you help me to learn more?