この木にしっかりつかまりなさい。

this (something or someone close to the speaker (including the speaker), or ideas expressed by the speaker)

tree; shrub; bush; wood; timber

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

tightly (holding on); firmly; securely; strongly (built); solidly; sturdily; steadily; properly; well; sufficiently; hard (working, etc.); fully; completely; reliably; dependably; levelheadedly; shrewdly; wisely; cleverly

to be caught; to be arrested; to hold on to; to grasp; to find (e.g. proof); to get (e.g. a taxi); to be detained by

to do