Sansom had mortgaged the croft to Heyward to secure a principal and interest of 28 12s. to be redeemed on the 8 June a year after the mortgage (i.e. to be redeemed within twelve months). Sansom now released the property to Heyward - i.e. released his equity of redemption of the land as he could or did not want to redeem the property by the appointed time a year later. In effect, the land was forfeited because Sansom did not redeem the principal and interest at the requisite time a year from the mortgage. It is probable that this forfeiture occurred before full equity of redemption was allowed in mortgages.

The hand
The hand is a fairish Secretary hand of the early seventeenth century.

The first element, the xp, indicates the chi-rho for christ

i.e. Rickmansworth in Hertfordshire

A deed indented or an indenture (or pair of indentures) are deeds with an indented ('wavy') edge - by comparison with this one, which has a straight edge at the top, that is, a deed poll.

quite claymed
By a quitclaim, a person renounced any right in property.