Each clue refers to a word with 5 vowels – one each of the letters A, E, I, O, and U. The vowels have been removed and the remaining consonants rearranged in alphabetical order.

E.g., GLNRT (9) = RULE OR PRINCIPLE gives REGULATION

QS (7) = GIANT CONIFEROUS TREE

DGL (8) = CONVERSATION

HPR (8) = FEELING OF GREAT ELATION

CDNT (9) = TEACHING AND LEARNING

CNST (9) = DETERMINED/RELENTESS

HRST (9) = GIVE PERMISSION

CNPRT (10) = PREVENTATIVE MEASURE

NPRTT (10) = STANDING

CFLLRW (11) = VEGETABLE

CLNPST (11) = CONJECTURE

LLRTTV (11) = PART OF ELECTROMAGNETIC SPECTRUM

BDMRSTX (12) = SKILLED WITH BOTH HANDS

Puzzle courtesy of Mensa member Peter Hooton