Clue: For rousing passion, unfinished symphony by Beethoven eclipses his fourth (6)
Answer: EROTIC
Explanation: Definition: For rousing passion
An envelope ('eclipses') of T ('his fourth' – i.e. the fourth letter of Bee**T**hoven') in EROIC[a] ('symphony by Beethoven' – actually his third) minus the last letter ('unfinished' – no, that's Schubert's eighth).