Regressive article presented by broadsheet on 1st April regarding former trade agreement (5)

'trade agreement' is the definition.
(I know that NAFTA is a free trade agreement)

'regressive article presented by broadsheet on 1st april' is the wordplay.
'regressive article' becomes 'na' (I can't explain this - if you can you should give a lot more credence to this answer).
'presented by' means one lot of letters go next to another.
'broadsheet' becomes 'FT' (Financial Times, broadsheet newspaper).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'nst april' becomes 'a' (nst letter of 'april').
'na'+'ft'+'a'='NAFTA'

'regarding former' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?