The affix yat (yaṃ) comes in the sense of 'being fitted with that', after the words 1. karma and 2. veṣa being in the Instrumental -3rd case in construction.,
This debars than. कर्मणा संपद्यते = कर्मण्यं शरीरम्, वेषेण संपद्यते = वेष्यो नटः ॥ For accent see 6.1.213.,