What is Spens clause?

A spens, Spens, spens clause, or Spens clause is a provision in a security which allows a borrower to repay the principal amount earlier than the contractual repayment date, on payment of a specified penalty, also referred to as a "make whole" payment, in excess of the principal of the security. In the case of a bond, this type of early repayment is often referred to as "calling the bond". A spens clause may also apply to a preference share that is redeemed on a winding up.