Solution for 3 September cryptic crossword clue

Ambassador taken in by Conservative conjecture (6)
Solution – theory

To get to the solution, you have to click on to their being a container clue involved as well as an abbreviation.  A common abbreviation for "ambassador" is HE – standing for His or Her Excellency.

The ambassador is "taken in by" – ie is found in the middle of a word that means "Conservative" – now in the UK which is the home of the cryptic crossword the Conservative party is known as the Tory party.

So if you put "he" into "tory" you get "theory" which matches the meaning for "conjecture".