… before strained situation leads to unjustified claim (10)
I believe the answer is:
pretension
'unjustified claim' is the definition.
'before strained situation' is the wordplay.
'before' becomes 'pre'.
'strained situation' becomes 'tension'.
'pre'+'tension'='PRETENSION'
'leads to' acts as a link.
(Other definitions for pretension that I've seen before include "Show" , "inappropriate style" , "Spurious claim, aspiration" , "The ostentation" , "A claim or aspiration (to something)" .)