The most common and most likely answer to this crossword clue is the 7 letter word CUT-OFF
I've seen this crossword clue in The Times
C
U
T
-
O
F
F
Buddy explains!
The straight part
We know that "firm limit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case firm limit = cut-off.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 CUT-OFF mean?
CUT-OFF adjective- Having had shirt sleeves or pantlegs shortened by cutting material from the end.
- The point at which something terminates or to which it is limited.
- A road, path or channel that provides a shorter or quicker path; a shortcut.
- A device that stops the flow of a current.
- A device for saving steam by regulating its admission to the cylinder (see quotation at cut-off).
- A cessation in a flow or activity.
- The player who acts directly before the player on the button pre-flop.
- (chiefly in the plural) shorts made by cutting off the legs from trousers
- A horizontal line separating sections of the page.