Instrument picked up in archaeobotany (4)
I believe the answer is:
oboe
'instrument' is the definition.
(oboe is a kind of instrument)
'picked up in archaeobotany' is the wordplay.
'picked up' says the letters should be written in reverse.
'in' indicates the answer is hidden within the clue.
'eobo' can be found hidden inside 'archaeobotany'.
'eobo' in reverse letter order is 'OBOE'.
(Other definitions for oboe that I've seen before include "source of notes" , "Orchestral instrument" , "Musical instrument" , "Cor anglais in its family" , "Double-reeded woodwind instrument" .)