It's terrible about half of lake having dried out (5)
I believe the answer is:
baked
'dried out' is the definition.
(cooked by dry heat)
'it's terrible about half of lake' is the wordplay.
'it's terrible' becomes 'bad' (similar in meaning).
'about' means one lot of letters goes inside another.
'half of' indicates taking half.
'lake' halved is 'ke'.
'bad' enclosing 'ke' is 'BAKED'.
'having' is the link.
(Other definitions for baked that I've seen before include "Got very hot in jacket" , "Cooked like a cake" , "Cooked (bread/cakes)" , "Dried" , "Cooked in an oven" .)