Chicken or fish sandwiches campaign (6)
I believe the answer is:
coward
'chicken' is the definition.
(similar in meaning)
'fish sandwiches campaign' is the wordplay.
'fish' becomes 'cod' (type of fish).
'sandwiches' indicates putting letters inside (to sandwich is to block something in).
'campaign' becomes 'war'.
'cod' going around 'war' is 'COWARD'.
'or' acts as a link.
(Other definitions for coward that I've seen before include "wimp" , "Noel -, twentieth-century actor, dramatist" , "Person without courage" , "Person who is excessively fearful, lacks courage" , "One lacks courage" .)