Peru, land perturbed about development in horology (8)
I believe the answer is:
pendular
'about development in horology' is the definition.
(as in pendulum - horology is the study of clocks)
'peru land perturbed' is the wordplay.
'perturbed' indicates an anagram.
'peru'+'land'='peruland'
'peruland' with letters rearranged gives 'PENDULAR'.
(Other definitions for pendular that I've seen before include "Hanging and swinging" , "Like a grandfather clock" .)