Unexpectedly caught in tuna war escalation (8)
I believe the answer is:
unawares
'unexpectedly' is the definition.
(I've seen this before)
'caught in tuna war escalation' is the wordplay.
'caught in' indicates a hidden word.
'UNAWARES' can be found hidden inside 'tuna war escalation'.
(Other definitions for unawares that I've seen before include "Unexpectedly, without noticing in new auras" , "Warn Esau (anag)" , "Unknowingly - by surprise" , "Be caught thus to be taken by surprise" , "in the dark" .)