Shy and tense (9)
I believe the answer is:
withdrawn
'shy' is the definition.
(withdrawn can mean shy or reserved)
'and tense' is the wordplay.
'and' becomes 'with'.
'tense' becomes 'drawn' (I've seen this before).
'with'+'drawn'='WITHDRAWN'
(Other definitions for withdrawn that I've seen before include "Pulled out of" , "Rather shy" , "taken out" , "Shy, reserved" , "Private" .)