General:
* Clue
* Suggestion
* Implication
* Intimation
* Indication
* Allusion
* Innuendo
* Whispering
* Imply
* Suggest
* Indicate
More specific:
* Subtle hint: Intimation, suggestion, insinuation
* Direct hint: Clue, indication, suggestion
* Indirect hint: Innuendo, implication, allusion
* Informal hint: Whispering, dropping a hint, giving a nudge
The best synonym for "hint" depends on the specific context and the nuance you want to convey.