Deceived about lake having flowed slowly (8)
I believe the answer is:
trickled
'flowed slowly' is the definition.
'trickled' can be an answer for 'flowed' (trickling is a kind of flowing). I am unsure of the 'slowly' bit.
'deceived about lake' is the wordplay.
I cannot quite see how this works, but
'about' could be 'c' (circa) and 'c' is present in the answer.
'lake' could be 'l' (geographical abbreviation) and 'l' is found within the answer.
The remaining letters 'triked' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'having' is the link.
Can you help me to learn more?
(Another definition for trickled that I've seen is " Ran".)