Upturned, the dirt is caked on – really bad (6)
I believe the answer is:
putrid
'really bad' is the definition.
'putrid' can be an answer for 'bad' (thesaurus). I am unsure of the 'really' bit.
'upturned the dirt is caked' is the wordplay.
'upturned' shows that the letters should be reversed in order.
'is caked' becomes 'up' (I can't justify this - if you can you should give a lot more credence to this answer).
'dirt'+'up'='dirtup'
'dirtup' reversed gives 'PUTRID'.
'on' is the link.
Can you help me to learn more?
(Other definitions for putrid that I've seen before include "contaminated" , "Turned" , "Decaying, really rotten" , "Rotting, fetid" , "High" .)