Suggestion in favour of concession set up on a lake (8)
I believe the answer is:
proposal
'suggestion' is the definition.
(I've seen this before)
'in favour of concession set up on a lake' is the wordplay.
'in favour of' becomes 'pro' (I've seen this before).
'concession' becomes 'sop' (sop is a kind of concession).
'set up' shows that the letters should be reversed in order.
'on' is a charade indicator (letters next to each other).
'lake' becomes 'l' (geographical abbreviation).
'sop' written backwards gives 'pos'.
'pro'+'pos'+'a'+'l'='PROPOSAL'
(Other definitions for proposal that I've seen before include "Suggestion put forward for consideration" , "Offer, of marriage say" , "put before the union?" , "Offer (to get spliced?)" , "Offer - suggestion" .)