Enjoy fibs - the first is most probable (9)
I believe the answer is:
likeliest
'most probable' is the definition.
(I've seen this before)
'enjoy fibs the first' is the wordplay.
'enjoy' becomes 'like' (like can mean to appreciate or enjoy something).
'fibs' becomes 'lies' (informal term for lies).
'first' says to take the initial letters.
The initial letter of 'the' is 't'.
'like'+'lies'+'t'='LIKELIEST'
'is' is the link.
(Other definitions for likeliest that I've seen before include "most promising" , "most plausible" , "Most probable" .)