Went ahead and held up, also – stole from (6)
I believe the answer is:
looted
'stole from' is the definition.
(I've seen this before)
'went ahead and held up' is the wordplay.
'went ahead' becomes 'del' (I can't justify this - if you can you should believe this answer much more).
'and' becomes 'too'.
'held' means one lot of letters goes inside another.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'del' going around 'too' is 'detool'.
'detool' written backwards gives 'LOOTED'.
'also' acts as a link.
This may not be right. It may be part of another bit of the clue.
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" .)