Final answer:
A Partial Release clause might be required in the security instrument for the construction loan to allow the developer to release specific lots from the lien of the loan as they are completed and sold.
Step-by-step explanation:
When a subdivision developer obtains a construction loan to build new houses on twenty lots, a type of clause that might be required in the security instrument for the construction loan is the Partial Release clause. This clause allows the developer to release specific lots from the lien of the loan as they are completed and sold. It provides flexibility for the developer by enabling them to sell individual lots and use the proceeds to repay a portion of the loan, reducing the overall debt burden.