Part of shower cap worn by heroine, oddly absent (6)
I believe the answer is:
leonid
'part of shower' is the definition.
'leonid' can be an answer for 'part' (I have seen 'Part of swarm' mean 'leonid' so perhaps 'part' could also mean 'leonid'). I'm not certain of the 'of shower' bit.
'cap worn by heroine oddly absent' is the wordplay.
'cap' becomes 'lid' (eg the lid of a bottle).
'worn by' indicates putting letters inside (outside letters are worn by those on the inside).
'oddly absent' indicates alternate letters (odd-numbered letters removed).
The alternate letters of 'heroine' are 'eon'.
'lid' going around 'eon' is 'LEONID'.
Can you help me to learn more?
(Other definitions for leonid that I've seen before include "- Brezhnev, Russian president" , "-- Brezhnev, former Soviet leader" , "bit of a shower" , "Small meteor" , "Brezhnev, for one" .)