Peer with face of thunder left in shock (7)
I believe the answer is:
startle
'shock' is the definition.
(startling is a kind of shocking)
'peer with face of thunder left' is the wordplay.
'peer' becomes 'stare' ().
'with' is an insertion indicator.
'face of' says to take the initial letters.
The first letters of 'thunder left' is 'tl'.
'stare' enclosing 'tl' is 'STARTLE'.
'in' is the link.
(Other definitions for startle that I've seen before include "Make jump" , "Frighten suddenly" , "Rock" , "Cause shock to" , "Shock (someone)" .)