Information about lake valley (4)
I believe the answer is:
glen
'valley' is the definition.
(glen is a kind of valley)
'information about lake' is the wordplay.
'information' becomes 'gen' (gen is a kind of information).
'about' indicates putting letters inside.
'lake' becomes 'l'.
'gen' going around 'l' is 'GLEN'.
(Other definitions for glen that I've seen before include "Narrow Scots valley" , "Depression in Scotland" , "Highland valley" , "Scottish mountain valley" , "Long narrow valley in Scotland" .)