Reticent about Tim turning up at the workplace (6)
I believe the answer is:
smithy
'the workplace' is the definition.
(smithy is a kind of workplace)
'reticent about tim turning up' is the wordplay.
'reticent' becomes 'shy' (I've seen this before).
'about' indicates putting letters inside.
'turning up' shows that the letters should be reversed in order.
'tim' backwards is 'mit'.
'shy' going around 'mit' is 'SMITHY'.
'at' is the link.
(Other definitions for smithy that I've seen before include "Old forge" , "Blacksmith's workshop" , "work area" , "Where 3s were made and fitted" , "Workplace for forging metal" .)