Profound transformation - like the tide (3,6)
I believe the answer is:
sea change
'profound transformation' is the definition.
(I've seen this before)
'the tide' is the wordplay.
I cannot really see how this works, but
'tide' could be 'sea' (I have seen 'The tide' mean 'sea' so perhaps 'tide' could also mean 'sea') and 'sea' is located in the answer.
The remaining letters 'change' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'like' is the link.
Can you help me to learn more?
(Other definitions for sea change that I've seen before include "Major transformation" , "Notable transformation" , "Significant or unexpected transformation - on the briny?" , "Profound transformation" , "Significant transformation of marine origin" .)