Most timid lead singer, okay during half time (6)
I believe the answer is:
shyest
'most timid' is the definition.
(I've seen this before)
'half time' is the wordplay.
'half' becomes 'shy' (I can't justify this - if you can you should believe this answer much more).
'time' becomes 'EST' (EST is an example).
'shy'+'est'='SHYEST'
'lead singer okay during' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for shyest that I've seen before include "Most bashful or self-conscious" , "withdrawn the most" , "Most retiring" , "Most diffident" , "shrinking the most?" .)