Beyond nervous — possibly frightened or terrified? (4,5)
I believe the answer is:
past tense
'possibly frightened or terrified?' is the definition.
('frightened' and 'terrified' are past tense verbs)
'beyond nervous' is the wordplay.
'beyond' becomes 'past' (to go beyond something is to go past it).
'nervous' becomes 'tense' (similar in meaning).
'past'+'tense'='PAST TENSE'
(Other definitions for past tense that I've seen before include "It expresses something that has happened" , "history?" , "Was perhaps" , "Form of verb showing that the action has already happened" , "Grammatical verb form" .)