Delectable years on corporation, though not at first (5)
I believe the answer is:
yummy
'delectable' is the definition.
(synonyms)
'years on corporation though not at first' is the wordplay.
'years on' becomes 'y' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'corporation' becomes 'tummy' (synonyms).
'though not at first' means to remove the first letter (the first letter is removed).
'tummy' with its first letter removed is 'ummy'.
'y'+'ummy'='YUMMY'
Can you help me to learn more?
(Other definitions for yummy that I've seen before include "Luscious" , "Like delicious food" , "Mmmmm!" , "Very tasty" , "That's truly scrumptious!" .)