High flier in trouble heading off to meet old singer (6)
I believe the answer is:
caruso
'singer' is the definition.
(opera singer Enrico Caruso)
'high flier in trouble heading off to meet old' is the wordplay.
'high flier in trouble' becomes 'icarus' (mythical figure who flew too close to the sun).
'heading off' means to remove the first letter.
'to meet' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'icarus' with its first letter taken away is 'carus'.
'carus'+'o'='CARUSO'
(Other definitions for caruso that I've seen before include "Enrico ---, operatic tenor" , "Enrico ...... was famous Italian tenor" , "Enrico . . . . . ., former tenor" , "Opera singer" , "Classical tenor" .)