Possible Clues:

• Not absolutely necessary
• Unnecessary
• Skill fellow primarily exuded translating Latin appendix, say
• Saving face, Neil Innes sat out, surplus to requirements
• Unnecessary seats in line to be shifted
• Spanish girl mailed one a line that's not really wanted
• Seen in a list perhaps, but it's not necessary
• Something that's only nice to have isn't in lease, unfortunately
• Not required
• As sentinel, I could be dispensable