Regret introducing stupid new article in trial - not fully thought through (11)
I believe the answer is:
rudimentary
'not fully thought through' is the definition.
'regret introducing stupid new article in trial' is the wordplay.
'regret' becomes 'rue' (synonyms).
'introducing' means one lot of letters goes inside another (some letters introduced or inserted into others).
'stupid' becomes 'dim' (similar in meaning).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'article in trial' becomes 'tary' (I can't explain this - if you can you should give a lot more credence to this answer).
'rue' going around 'dim' is 'rudime'.
'rudime'+'n'+'tary'='RUDIMENTARY'
Can you help me to learn more?
(Other definitions for rudimentary that I've seen before include "Primitive" , "Basic" , "Limited to basics" , "in the early stages" , "Immature" .)