The most common and most likely answer to this crossword clue is the 8 letter word DOORJAMB
D
O
O
R
J
A
M
B
More clues leading to the result DOORJAMB
- Yellow pack arriving in birthday post
- Entrance part of party crowd in gilded ball
- Tricky situation encountered in raising large family – find fixed post to latch onto
- Side member makes an entrance to improvise in soundcheck
- Carry out alternative to preserve black sidepiece
- Perform / sing with boy — one that can play a supporting role?
- Fret over having stoppage in post
Buddy explains!

The straight part
We know that "one that can play a supporting role?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one that can play a supporting role? = doorjamb.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.