Even I, perhaps, could become nervous (12)
I believe the answer is:
apprehensive
'nervous' is the definition.
(synonyms)
'even i perhaps could become' is the wordplay.
'could become' indicates an anagram.
'even'+'i'+'perhaps'='eveniperhaps'
'eveniperhaps' with letters rearranged gives 'APPREHENSIVE'.
(Other definitions for apprehensive that I've seen before include "Worried" , "Seven happier (anag.)" , "Fearful, anxious" , "Feeling anxiety or fear about future events" , "Uneasy, anxious" .)