Can my club play an overseas professional?

Yes, with the CGL Board's prior consent. Under the CGL By-laws:

• Who counts as an overseas professional: a cricketer who was neither born in nor is a permanent resident of South Africa, has played most of their cricket in another country, and has been paid directly as a full-time cricketer in that country.
• Limit: a club may play 1 overseas professional in a league team, after getting the Board's consent. The Board may allow more than one in particular circumstances.
• Penalty for playing one without consent: the club loses the points for that match, is fined R500 and loses a further 3 points, and the player is suspended for a match.