The most common and most likely answer to this crossword clue is the 8 letter word PROTRACT
I've seen this crossword clue in The Daily Telegraph
P
R
O
T
R
A
C
T
More clues leading to the result PROTRACT
- Extend series of organs, etc, having expert as leader
- Extend piece of writing with publicist's introduction
- Drag out religious pamphlet written by an expert?
- Make longer right turn after quiet hill-climbing
- Continue being in favour of diplomacy when interrupted by king
- Extend piece of writing provided by publicist
- Extend agreement to cover results over target range, initially
- Extend professional area
- Pamphlet by one getting paid is to keep going
- Sermon by one paid to go on a bit
Buddy explains!

The straight part
We know that "keep going" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case keep going = protract.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.
What does PROTRACT mean?
PROTRACT verb- To draw out; to extend, especially in duration.
- To use a protractor.
- To draw to a scale; to lay down the lines and angles of, with scale and protractor; to plot.
- To put off to a distant time; to delay; to defer.
- To extend; to protrude.