Nervous, tense setter's supported by papers (5)
I believe the answer is:
timid
'nervous' is the definition.
(I've seen this before)
'tense setter's supported by papers' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'setter's' becomes 'im' (referring to the crossword setter).
'supported by' means one lot of letters go next to another (in a down clue, some letters hold up others).
'papers' becomes 'ID' (short for identification papers).
't'+'im'+'id'='TIMID'
(Other definitions for timid that I've seen before include "afraid to speak out?" , "Pusillanimous" , "Apprehensive and unassertive" , "Gutless" , "Nervous and easily alarmed" .)