Partly glad I thought about such a wave (5)
I believe the answer is:
tidal
'a wave' is the definition.
(tidal wave is a kind of wave)
'partly glad i thought about' is the wordplay.
'partly' indicates a hidden word.
'about' says the letters should be written backwards.
'ladit' can be found hidden inside 'glad i thought'.
'ladit' written backwards gives 'TIDAL'.
'such' is the link.
(Other definitions for tidal that I've seen before include "To do with movement of seas" , "Relating to the rise and fall of the sea" , "Like the sea" , "Going back and forth" , "Affected by changes in sea level" .)