Expert turning up in hotel bar (4)
I believe the answer is:
able
'expert' is the definition.
(I've seen this before)
'turning up in hotel bar' is the wordplay.
'turning up' shows that the letters should be reversed in order.
'in' indicates a hidden word.
'elba' can be found hidden inside 'hotel bar'.
'elba' in reverse letter order is 'ABLE'.
(Other definitions for able that I've seen before include "In a position or competent to" , "Showing skill" , "Competent as, say, sailor" , "See 21" , "See 10" .)