مِّن مَّسَدٍ

مِّن مَّسَدٍ is a phrase (شِبْهُ الجُمْلَةِ) consisting of a particle and a noun

PhraseParticle/NounNoun Particle 
 شِبْهُ الجُمْلَةِجَارٌ وَمَجْرُوْرٌاسْمٌ مَجْرُوْرٌحَرْفُ جَرٍّ
PhraseCompoundGenitive NounParticle of pulling down
  
مِّن مَّسَدٍ=مَّسَدٍ+مِّن
from palm fiberpalm fiberfrom
Surah/Below is the only verse in the holy Quran containing the compoundمِّن مَّسَدٍ
Aayat
111-5In her neck a rope of palm fiberفِيْ جِيْدِهَا حَبْلٌ مِّن مَّسَدٍ