Look after that rising river with old form of technology (3,2,2)
I believe the answer is:
see to it
'look after that' is the definition.
(to see to something is to look after or handle it)
'rising river with old form of technology' is the wordplay.
'rising' shows that the letters should be reversed in order (going up in a down clue).
'river' becomes 'tees' (River Tees).
'with' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'form of technology' becomes 'IT' (short for information technology).
'tees' back-to-front is 'seet'.
'seet'+'o'+'it'='SEE TO IT'
(Another definition for see to it that I've seen is " Make sure".)