Childish to unveil work between the beginning and end of June (8)
I believe the answer is:
juvenile
'childish' is the definition.
(I've seen this before)
'unveil work between the beginning and end of june' is the wordplay.
'work' indicates an anagram.
'between' is an insertion indicator.
'the beginning and end of' suggests removing the centre.
'june' with its middle taken out is 'je'.
'unveil' with letters rearranged gives 'uvenil'.
'uvenil' placed inside 'je' is 'JUVENILE'.
'to' acts as a link.
(Other definitions for juvenile that I've seen before include "Of young people" , "Young offender" , "Youth" , "Infantile" , "Young, immature" .)