What does the hyphen in this dictionary entry mean?
In official Japanese-language typesetting, which Unicode character should it be? I suspect it is not the minus sign character on most English-language keyboard.
It's just a hyphen to split the word stem from the suffix 家. It's not written that way in normal text, but you do see it in dictionaries or word lists.
To answer your typographic question, my local electronic copy of the Daijirin dictionary does indeed use the regular minus or hyphen character, ASCII decimal code 45, Unicode point U+002D HYPHEN-MINUS. My other electronic dictionary, Shogakukan's 国語【こくご】大【だい】辞典【じてん】, uses Unicode point U+2010 HYPHEN.
Online versions of Daijirin don't seem to use hyphens at all. This dictionary doesn't have an entry for 努力家, so for comparison, here's the Daijirin entry for 政治家, with no hyphens or spaces to show the suffix, and here's the Daijisen entry for 政治家 showing the Unicode HYPHEN character to show the suffix. I note that Daijisen is also published by Shogakukan, so this publisher might just prefer this character.