Irregular form of PC's radio (8)
I believe the answer is:
sporadic
'irregular' is the definition.
(similar in meaning)
'form of pc's radio' is the wordplay.
'form of' indicates an anagram (the letters need to be in another 'form').
'pcs'+'radio'='pcsradio'
'pcsradio' anagrammed gives 'SPORADIC'.
(Other definitions for sporadic that I've seen before include "Having separate patches" , "Fitful, intermittent" , "Random" , "Happening irregularly" , "Isolated; intermittent" .)