Hi, Dylan,
In your other post, you said 4ac. This is a two-word phrase (6,4). The answer appears under the first word. There is a second entry for this word, which refers to an alternative spelling. This is a Scottish word meaning “strength”. If you were to an an “o” to the second word, you would get an Australian slang word for cheap wine. The whole phrase is a terrible weapon.
For 41ac, remember who the setter is today. You have a two-letter possessive pronoun referring to the setter, plus the last letter of “lengthening”, all reversed, to give a word meaning “exercises”. The final letter is a clash.
For 12 dn, think of a five-letter word very much like the answer to 3dn, meaning “problems”. In 46ac, the sixth letter is a clash. Think of a five-letter word meaning “mate” (cockney rhyming slang), remove the “h”, then add a common abbreviation for “green” in the environmental sense, and reverse the lot.
Hope this helps. There are indeed 13 clashes.