The most common and most likely answer to this crossword clue is the 8 letter word FASTNESS
F
A
S
T
N
E
S
S
More clues leading to the result FASTNESS
Buddy explains!

The straight part
We know that "Keep/pace" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case keep/pace = fastness.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 FASTNESS mean?
FASTNESS noun- A secure or fortified place; a stronghold, a fortress.
- The state of being fast.
- The ability of a dye to withstand fading.