Seven clues contain a redundant word, each defining one unclued light. These seven unclued lights all undergo partial 1 across (in Collins) before entry, in a consistent manner. Resulting grid entries are not real words. Unchecked and cross-checking letters in all eight unclued lights could give: NEWS — I’LL HINT THIS: CRUX’S LATIN
 

Across

12    Physicist’s drole gibe cracking up virgin (9, two words)
13    Love time off to produce plant sheaths (6)
16    Decide crazy American quits US city (6)
17    Old claim Reading’s awful (7)
20    Male’s arms twirling (4)
22    A hero, one up to revel in high spirits (8)
24    Points taken by genius...