Sorry for worms twisting in heap (8)
I believe the answer is:
pitiable
'sorry' is the definition.
(thesaurus)
'for worms twisting in heap' is the wordplay.
'for worms' becomes 'bait' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'twisting' is a reversal indicator (letters twist back).
'in' is an insertion indicator.
'heap' becomes 'pile' (synonyms).
'bait' in reverse letter order is 'tiab'.
'tiab' placed into 'pile' is 'PITIABLE'.
Can you help me to learn more?
(Other definitions for pitiable that I've seen before include "It's not to be envied" , "Wretched" , "Deserving contempt" , "Deserving compassion" , "Contemptible" .)