Transformation in the main? (3,6)
I believe the answer is:
sea change
'transformation' is the definition.
(I've seen this before)
'main?' is the wordplay.
I cannot quite understand how this works, but
'main?' could be 'sea' (the main is an old name for the sea) and 'sea' is found 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...
'in the' acts as a link.
Can you help me to learn more?
(Other definitions for sea change that I've seen before include "Significant or unexpected transformation - on the briny?" , "Profound transformation" , "Notable transformation" , "Significant transformation of marine origin" , "Major transformation" .)