Parentheses around a letter mean that it has to be omitted before the word will fit in the grid. The word or phrase the omitted letters spell is given below, and mystery words are in italics.

Across

1. GROUND
2. RECE (S) SION
3. LENS
4. MEDUSA
5. SIMA
6. PORT (A) L
7. TRITONE
8. POET
9. ECLA (I) R
10. (N) ATRON
11. SNOW
12. NOSHED
13. PABLO
14. INCUS
15. RIBALD
16. CHANCE
17. NORGE
18. S (T) ENCIL
19. STO (V) ER
20. CACHE
21. SCANT
22. FOREM (A) N
23. HOG

Down

1. G (L) ISTEN
2. BARON
3. ROAR
4. COLL (E) GE
5. TONSIL
6. WO (N) DERFUL
7. (T) ITANIC
8. SCONE
9. MORON
10. HEARD
11. NANAS
12. CANCERS
13. PET
14. HUNCH
15. MEMO
16. PRESCIENCE
17. ROOD
18. REL (I) SHED
19. TENPINS
20. CO (N) SULT
21. SABOTAG (E)

The omitted letters spell: Saint Valentine