Gary isn't cast in 1960s' TV series (8)
I believe the answer is:
stingray
'1960s' tv series' is the definition.
I can't tell whether this defines the answer.
'gary isn't cast' is the wordplay.
'cast' is an anagram indicator (letters are dispersed or cast around).
'gary'+'isnt'='garyisnt'
'garyisnt' is an anagram of 'STINGRAY'.
'in' is the link.
Can you help me to learn more?
(Other definitions for stingray that I've seen before include "TV show" , "Dangerous fish" , "swimmer" , "Fish with venomous tail" , "Marine creature with venomous tail" .)