The most common and most likely answer to this crossword clue is the 6 letter word LONGER
I've seen this crossword clue in The Guardian
L
O
N
G
E
R
Buddy explains!
The straight part
We know that "going into extra time" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case going into extra time = longer.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 LONGER mean?
LONGER adjective- Having much distance from one terminating point on an object or an area to another terminating point (usually applies to horizontal dimensions; see Usage Notes below).
- Having great duration.
- Seemingly lasting a lot of time, because it is boring or tedious or tiring.
- Not short; tall.
- Possessing or owning stocks, bonds, commodities or other financial instruments with the aim of benefiting of the expected rise in their value.
- Of a fielding position, close to the boundary (or closer to the boundary than the equivalent short position).
- (of a ball or a shot) Landing beyond the baseline, and therefore deemed to be out.
- Occurring or coming after an extended interval; distant in time; far away.
- Over a great distance in space.
- For a particular duration.
- For a long duration.
- One who longs or yearns for something.