Lout cried occasionally — that's clear (5)
I believe the answer is:
lucid
'clear' is the definition.
(similar in meaning)
'lout cried occasionally' is the wordplay.
'occasionally' indicates alternate letters (letters taken at regular intervals or occasions).
'lout'+'cried'='loutcried'
The alternating letters of 'loutcried' are 'LUCID'.
'that's' acts as a link.
(Other definitions for lucid that I've seen before include "Clear, intelligible" , "Bright; sane" , "Rational, clear" , "Clearly expressed and altogether rational" , "Thinking clearly" .)