Wind and spray both sides crossing midpoint of dam (7)
I believe the answer is:
mistral
'wind' is the definition.
(mistral is a kind of wind)
'spray both sides crossing midpoint of dam' is the wordplay.
'spray' becomes 'mist' (misting is a kind of spraying).
'both sides' becomes 'rl' (I've seen this in other clues).
'crossing' is an insertion indicator.
'midpoint of' indicates the central letters.
The centre of 'dam' is 'a'.
'rl' going around 'a' is 'ral'.
'mist'+'ral'='MISTRAL'
'and' is the link.
(Other definitions for mistral that I've seen before include "Violent northeast wind of southern France" , "Strong wind down the 20 valley" , "A harsh blow" , "Famous wind in the Rhone Valley blowing towards the Med" , "French wind" .)