Split up and put down each row's thematic group (7)
I believe the answer is:
disband
'split up' is the definition.
(thesaurus)
'put down each row's thematic group' is the wordplay.
I cannot really understand how this works, but
'down' could be 'd' and 'd' is found in the answer.
'group' could be 'band' (band can mean a group of people) and 'band' is found in the answer.
The remaining letters 'is' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'and' acts as a link.
Can you help me to learn more?
(Other definitions for disband that I've seen before include "Dissolve" , "Cease to be a group" , "Break up as a group" , "shed" , "Scatter" .)