Will - one that's written with wife oddly leaving photo (6)

'photo' is the definition.
(I have seen 'Personal photo' mean 'selfie' so perhaps 'photo' could also mean 'selfie')

'will one that's written with wife oddly' is the wordplay.
'will' becomes 'self' (I can't explain this - if you can you should give a lot more credence to this answer).
'one that's written with' says to put letters next to each other.
'oddly' means one should take alternating letters (letters in odd-numbered positions).
The alternate letters of 'wife' are 'ie'.
'self'+'ie'='SELFIE'

'leaving' acts as a link.

Can you help me to learn more?