Pharaoh dips into sea and a lake in the morning (9)
I believe the answer is:
matutinal
'in the morning' is the definition.
(I've seen this before)
'pharaoh dips into sea and a lake' is the wordplay.
'pharaoh' becomes 'tut' (colloquial name for Tutankhamun).
'dips into' is an insertion indicator.
'sea' becomes 'main' ('main' can be a synonym of 'sea'**).
'and' means one lot of letters go next to another.
'lake' becomes 'l'.
'tut' put inside 'main' is 'matutin'.
'matutin'+'a'+'l'='MATUTINAL'
(Other definitions for matutinal that I've seen before include "before noon" , "Early" , "Of the morning" .)