Friend in France surrounded by upset workers shows inner strength (7)
I believe the answer is:
stamina
'inner strength' is the definition.
(I've seen this in another clue)
'friend in france surrounded by upset workers' is the wordplay.
'friend in france' becomes 'ami' ('friend' in French).
'surrounded by' means one lot of letters goes inside another.
'upset' shows that the letters should be reversed in order.
'workers' becomes 'ants' (I've seen this before).
'ants' backwards is 'stna'.
'ami' inserted into 'stna' is 'STAMINA'.
'shows' acts as a link.
(Other definitions for stamina that I've seen before include "Ability for sustained effort" , "resistance" , "legs" , "This man owes his strength" , "Vigour" .)