tiger

have (or catch) a tiger by the tail = ride a tiger.

☞ A similar difficulty confronts those who have a wolf by the ears (seewolf).

1979Peter DriscollPangolin You're taking on an organization with reserves you know nothing about. How do you know you won't be catching a tiger by the tail?

a paper tiger: seepaper.

ride a tiger take on a responsibility or embark on a course of action which subsequently cannot safely be abandoned.

☞ The expression comes from the Chinese proverb 'He who rides a tiger is afraid to dismount'.

1940Daily Progress (USA) I believe that Hitler is riding a tiger in trying to keep all Europe under control by sheer force.

a tiger in your tank energy, spirit, or animation.

☞ This expression originated as a 1960s advertising slogan for Esso petrol: 'Put a tiger in your tank'.