Require even one-eyed deputy to join (4)
I believe the answer is:
need
'require' is the definition.
(I know that require can be written as need)
'even one-eyed deputy to join' is the wordplay.
'even' means one should take alternating letters (even-numbered letters are used).
'deputy' becomes 'd' (this could be a standard abbreviation I've not previously seen).
'to join' is a charade indicator (letters next to each other).
'one'+'eyed'='oneeyed'
The alternate letters of 'oneeyed' are 'nee'.
'nee'+'d'='NEED'
Can you help me to learn more?
(Other definitions for need that I've seen before include "destitute state" , "Penury" , "'miss'" , "Require (as essential)" , "state of distress" .)