### Clue: Sacred word such as amen's first and last (5)
### Answer: OMEGA 
 ### Explanation: Definition: last
 OM(in Hinduism and Buddhism, a sacred syllable used as a mantra) + EG(abbrev. for "exempli gratia";for example;such as) + **the 1st letter of**(…'s first) "*amen*".
Defn: … of a series.