Related Clues:

• Worked out a sum
• Pitched in
• Found the sum
• Read into
• Do a summer's work?
• Construe
• Compute, sometimes
• Write, as a P.S.
• Offer as a bonus
• Make a contribution
• Write in a postscript, e.g.
• Use a '+'
• Calculate the total
• Cookbook directive
• ___ insult to injury