
1) Digressions in a speech 2) French television talk show 3) Parts of some Irish names 4) What links the theme entries
Found on
https://www.crosswordclues.com/clue/apostrophes
[talk show] Apostrophes was a live, weekly, literary, prime-time, talk show on French television created and hosted by Bernard Pivot. It ran for fifteen years (724 episodes) from January 10, 1975 to June 22, 1990, and was one of the most watched shows on French television (around 6 million regular viewers). It was broadcast on Friday nights...
Found on
http://en.wikipedia.org/wiki/Apostrophes_(talk_show)

a raised comma used to denote either possession or contraction
Found on
https://www.encyclo.co.uk/local/20403
No exact match found.