Explanation:

- One who does a thing for pleasure and not as a profession is often referred to as someone who engages in activities for enjoyment rather than for financial gain or career advancement.

- Option 1: Performer

- A person who entertains an audience, typically as part of a professional career in the arts.

- Not necessarily linked to doing it purely for pleasure.

- Option 2: Amateur

- Refers to someone who engages in a pursuit, especially a sport or art, on an unpaid rather than a professional basis.

- Originates from the Latin word 'amator' meaning 'lover of'.

- Fits the definition given.

- Option 3: Professional

- Involves someone engaged in a specified activity as their main paid occupation.

- Opposite of the given definition.

- Option 4: Ascetic

- Describes a person who leads a life of strict self-discipline and abstention from pleasure, often for religious reasons.

- Not related to leisure activities.