The most common and most likely answer to this crossword clue is the 7 letter word GRADUAL
I've seen this crossword clue in Financial Times
G
R
A
D
U
A
L
More clues leading to the result GRADUAL
- Allow a pair of books to be removed step by step
- Applaud arguments, some backing moderate
- Gentle drug a lab, not British, manufactured
- Gentle praise echoed after seizure reduced
- Gentle old king has a double
- Step-by-step rag for playing as a pair
- Slow guard, out of position by a lake
- Even admire fabulous ship nearly capsizing
- A guard at ease beginning to linger by steps?
- Gentle girl, oddly, had a fight reported
Buddy explains!

The straight part
We know that "step by step" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case step by step = gradual.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 GRADUAL mean?
GRADUAL noun- An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps.
- A service book containing the musical portions of the Mass.
- Proceeding or advancing by small, slow, regular steps or degrees