Unfortunately, there is no mechanism to apply for less tax to be withheld.
But, there are two options you could consider. The first option is to convert your RRSP to an RRIF sooner than age 71, so you have to take out less (and pay less in taxes) each year; you can do this starting at age 55. The RRIF is a collection of investments similar to an RRSP that you draw down by the mandated amount and, depending on how long you live after retirement, could run out before you die (because you started withdrawals early). Since you likely have other sources of income, this may not be a problem for you.
The second option is to convert your RRSP into an annuity. An annuity is a form of insurance that guarantees a fixed sum of money is paid to you each year for life or, for a specified amount of time. Annuity payments from an RRSP will be taxed as income in the year you receive them.
