Hard job retaining first opening for rock singer (9)
I believe the answer is:
chorister
'rock singer' is the definition.
'chorister' can be an answer for 'singer' (singer in a choir). I'm unsure of the 'rock' bit.
'hard job retaining first opening for' is the wordplay.
'hard' becomes 'ist' (I can't explain this - if you can you should believe this answer much more).
'job' becomes 'chore' (synonyms).
'retaining first' becomes 'r' (ist letter of 'retaining').
'opening for' means one lot of letters goes inside another (some letters open up to accept other letters).
'chore'+'r'='chorer'
'ist' going into 'chorer' is 'CHORISTER'.
Can you help me to learn more?
(Other definitions for chorister that I've seen before include "Boy singing" , "Boy singer" , "Church, cathedral singer" , "Choirboy or girl" , "Boy in church" .)