Went ahead and held up, also - stole from (6)
I believe the answer is:
looted
'stole from' is the definition.
(I've seen this in another clue)
'went ahead and held up' is the wordplay.
'went ahead' becomes 'del' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' becomes 'too'.
'held' indicates putting letters inside.
'up' says the letters should be written backwards (in down clue: letters go upwards).
'del' placed around 'too' is 'detool'.
'detool' backwards is 'LOOTED'.
'also' acts as a link.
Can you help me to learn more?
(Other definitions for looted that I've seen before include "Plundered and robbed" , "having taken part in a robbery" , "Sacked" , "Ransacked, plundered" , "stole stuff" .)