Lie back on odd occasions, finding unexpected release (4)
I believe the answer is:
leak
'unexpected release' is the definition.
(eg an unexpected release of information)
'lie back on odd occasions' is the wordplay.
'on odd occasions' indicates alternate letters (the odd-numbered letters are used).
'lie'+'back'='lieback'
The alternating letters of 'lieback' are 'LEAK'.
'finding' is the link.
(Other definitions for leak that I've seen before include "Seep; disclose" , "Escape - make (confidential information) known" , "Unauthorised disclosure of confidential information" , "Disclose (secrets)" , "Accidental hole allowing liquid to escape" .)