Turned on, tense and worried? Write music (6)
I believe the answer is:
notate
'write music' is the definition.
(I've seen this in another clue)
'turned on tense and worried?' is the wordplay.
'turned' shows that the letters should be reversed in order.
'tense' becomes 't' (abbreviation used in many dictionaries).
'and' says to put letters next to each other.
'worried?' becomes 'ate' (something worrying may eat someone up).
'on' back-to-front is 'no'.
'no'+'t'+'ate'='NOTATE'
(Other definitions for notate that I've seen before include "Put down in writing" , "Mark up" , "Express in symbols" , "Set down (in symbols)" , "Write special signs" .)