Applying a markup command to only part of a word

[Mike Stickles]

I'm currently working on resetting some church music where only the 
first and last three or four verses are actually scores; everything in 
the middle is just text, with underlining used to show where the 
"movement" comes in (every verse follows an identical pattern except for 
the ending verses).

Unfortunately, some of these have only part of the word underlined, as 
the "movement" comes on a specific syllable. For example, in this 
half-verse:

"For my brethren and companions' sake"

the vocal movement comes on the "pan" in "companions'", so I need to 
only underline that syllable. But I have not been able to do it without 
introducing spaces on either side of the syllable. Is there a way to do 
this while keeping the word together?