What does the cryptic crossword clue "Defensive attitude is let in game yet could change (5,9)" mean?

The wordplay uses an anagram. anagram of IS + LET + IN + GAME + YET = SIEGEMENTALITY The answer is SIEGEMENTALITY.

Defensive attitude is let in game yet could change (5,9)

Daily Mail Cryptic #17382 | 8 Down | 2024-06-18 flower