Implicating shush → gesture
Link to implication

Reason:

Shush, the index finger of one hand is extended and placed vertically in front of the lips, with the remaining fingers curled toward the palm with the thumb forming a fist; used to demand or request silence from those to whom it is directed. Can be silent or accompanied by an audible 'Sssh!' sound which alone has the same meaning.

EDIT: The tag implication shush -> gesture (forum #277373) has been rejected by @NotMeNotYou.