Stop from trembling in fear behind king (7)
I believe the answer is:
refrain
'stop' is the definition.
(I've seen this before)
'trembling in fear behind king' is the wordplay.
'trembling' is an anagram indicator.
'behind' says to put letters next to each other.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'in'+'fear'='infear'
'infear' is an anagram of 'efrain'.
'efrain' after 'r' is 'REFRAIN'.
'from' is the link.
(Other definitions for refrain that I've seen before include "Repeating line in a song, poem" , "The repeated lines at the end of verses" , "Cease - repeated phrase" , "Desist, abstain" , "tune" .)