What does the cryptic crossword clue "Pledge to welcome head of government that’s put up in sailing ship (7)" mean?

The wordplay uses acrostic. PM (synonym="head of government") in TOAST (synonym="pledge") = TOPMAST The answer is TOPMAST.

Pledge to welcome head of government that’s put up in sailing ship (7)

Guardian Cryptic #29602 | 7 Down | 2025-01-27 flower