The clue "Command+S, on a Mac" refers to a keyboard shortcut that is widely used in many applications on Macintosh computers. The shortcut Command+S is typically used to **save** a file or document.
Given that "save" is only four letters long and fits with the common structure of crossword answers, the likely answer to this clue is:
**SAVE**
### Solving Process:
1. **Identification of Keywords**: The clue clearly indicates it is related to a command on a computer, specifically a Mac, which narrows down the context.
2. **Knowledge of Computer Shortcuts**: Familiarity with Mac shortcuts led to a direct recognition that Command+S is the shortcut for saving files.
3. **Length of the answer**: Ensuring the answer fits within any existing letters in the crossword grid helps confirm this guess.
### Tips for Crossword Solving:
- **Knowledge of Common Shortcuts**: Familiarize yourself with common keyboard shortcuts since they often appear in tech-related clues.
- **Think About Context**: Consider the context of clues; tech terms might correlate with recent trends or terminology in the digital world.
- **Letter Constraints**: Use the letters you already have in the crossword to help confirm or rule out potential answers quickly.
Based on this reasoning, if no letters were provided, **SAVE** is a strong and logical answer to the clue.