Tense exploit held up by Austrian artist (5)
I believe the answer is:
klimt
'austrian artist' is the definition.
(I've seen this in another clue)
'tense exploit held up by' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'exploit' becomes 'milk' (to milk something is to exploit its potential).
'held up' is a reversal indicator.
'by' means one lot of letters go next to another.
'milk' written backwards gives 'klim'.
't' after 'klim' is 'KLIMT'.
(Other definitions for klimt that I've seen before include "Gustav - - , Austrian symbolist" , "Austrian artist" , "Gustav -, nineteenth to twentieth century Austrian painter" , "Austrian painter influenced by Art Nouveau" .)