Inspect radio picking up ranges of frequencies (7)
I believe the answer is:
spectra
'ranges of frequencies' is the definition.
(plural of 'spectrum')
'inspect radio picking up' is the wordplay.
'picking up' indicates a hidden word (the clue holds the solution).
'SPECTRA' is hidden in the letters of 'inspect radio'.
(Other definitions for spectra that I've seen before include "Bands of refracted colour" , "Carpets (anag.)" , "After-images" , "Whole ranges" , "Ranges of light wavelengths" .)