Remarked that the cake was plain, perhaps (7)
I believe the answer is:
noticed
'remarked' is the definition.
(noticing is a kind of remarking)
'the cake was plain perhaps' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'cake' could be 'ice' (I have seen 'Top cake' mean 'ice' so perhaps 'cake' could also mean 'ice') and 'ice' is found within the answer.
The remaining letters 'nod' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'that' is the link.
Can you help me to learn more?
(Other definitions for noticed that I've seen before include "Perceived or observed" , "Marked" , "Clocked" , "Became aware of" , "regarded" .)