More nervous European’s fantastic grid contains surprise ending (6)
I believe the answer is:
edgier
'more nervous' is the definition.
('edgy' can be a synonym of 'nervous')
'european's fantastic grid contains surprise ending' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'fantastic' is an anagram indicator.
'contains' means one lot of letters goes inside another.
'ending' suggests the final letters.
The final letter of 'surprise' is 'e'.
'grid' anagrammed gives 'dgir'.
'dgir' placed around 'e' is 'dgier'.
'e'+'dgier'='EDGIER'
(Other definitions for edgier that I've seen before include "More jittery" , "More nervous" , "More brittle" .)