Coax California Joe to eat a head of lettuce (6)
I believe the answer is:
cajole
'coax' is the definition.
(I know that coax can be written as cajole)
'california joe to eat a head of lettuce' is the wordplay.
'california' becomes 'ca' (abbreviation).
'to eat' means one lot of letters goes inside another.
'a head of' indicates taking the first letters.
The first letter of 'lettuce' is 'l'.
'joe' placed around 'l' is 'jole'.
'ca'+'jole'='CAJOLE'
(Other definitions for cajole that I've seen before include "Persuade by coaxing" , "Wheedle, sweet-talk" , "'Coax, inveigle (6)'" , "Urge by gentle flattery" , "Wheedle, try to persuade" .)