Tedium from some taxi unnecessarily turning up (5)
I believe the answer is:
ennui
'tedium' is the definition.
(I know that tedium can be written as ennui)
'some taxi unnecessarily turning up' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'turning up' says the letters should be written in reverse.
'iunne' can be found hidden inside 'taxi unnecessarily'.
'iunne' in reverse letter order is 'ENNUI'.
'from' is the link.
(Other definitions for ennui that I've seen before include "Boredom, tedium" , "Feeling of weariness or boredom" , "tiredness" , "bore" , "Weariness with life" .)