The most common and most likely answer to this crossword clue is the 7 letter word AUGMENT
A
U
G
M
E
N
T
More clues leading to the result AUGMENT
- Increase time beyond a month, chaps
- Get bigger people to stand in for us during month
- Add to men relieving us in some 31 days?
- Swell chaps replacing us in a month
- Swell fellows standing in for us during holiday month?
- Swell chaps ending in debt after a month
- Add to gold metal initially imported by man
- To grow, men replace us in a month
- Increase millions invested by chap chasing gold
- Soldiers, during month after US withdrawal, increase
Buddy explains!

The straight part
We know that "Add to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case add to = augment.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 AUGMENT mean?
AUGMENT noun- (grammar) In some Indo-European languages, a prefix e- (a- in Sanskrit) indicating a past tense of a verb.
- (grammar) In some Bantu languages, an additional vowel prepended to the noun prefix.
- An increase.
- To increase; to make larger or supplement.
- To grow; to increase; to become greater.
- To slow the tempo or meter, e.g. for a dramatic or stately passage.
- To increase an interval, especially the largest interval in a triad, by a half step (chromatic semitone).
- (grammar) To add an augment to.