Network admits staff looked in pain (8)
I believe the answer is:
grimaced
'looked in pain' is the definition.
(a grimace is a pained facial expression)
'network admits staff' is the wordplay.
'network' becomes 'grid' (grid is a kind of network).
'admits' means one lot of letters goes inside another.
'staff' becomes 'mace' (a mace is a ceremonial staff or stick).
'grid' enclosing 'mace' is 'GRIMACED'.
(Other definitions for grimaced that I've seen before include "Pulled a face" , "Scowled" , "didn't look happy" , "Made an ugly face" , "Made contorted face over decigram" .)