well, i think a ship that is a tender, is part of defination 3, (which should read a person or thing that tends)

Tenders, like tug boats, are ships that have specific duties. Tug boats tug barges (and in NY Harbor, tug large boats in and out of berths/channels (NYC harbor is a combinatin fyord/tidal estuary.. silt is a big problem. (see news stories about the Intrepid)

Tenders are boats that tend to ship that are not berthed at pier.

Still, its a very good call! aren't there also rail road cars called tenders? (same purpose as the ships, but another use of the word)

my other obsession