Hot drink yours truly had lacking flavour (7)
I believe the answer is:
insipid
'lacking flavour' is the definition.
(I've seen this before)
'hot drink yours truly had' is the wordplay.
'hot' becomes 'in' (both can mean fashionable).
'drink' becomes 'sip' (sipping is a kind of drinking).
'yours truly had' becomes 'I'd' ('I had', referring to the crossword setter).
'in'+'sip'+'id'='INSIPID'
(Other definitions for insipid that I've seen before include "dry" , "Bland, flavourless" , "Tasteless" , "Wishy-washy" , "Lacking in flavour or interest" .)