The most common and most likely answer to this crossword clue is the 7 letter word MAKE-DO
I've seen this crossword clue in The Guardian
M
A
K
E
-
D
O
More clues leading to the result MAKE-DO
Buddy explains!
The straight part
We know that "substitute/? (4-2)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case substitute/? (4-2) = make-do.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 MAKE-DO mean?
MAKE-DO noun- A temporary or makeshift expedient.
- Improvised, makeshift