Gift item — oddly, with jam on top (7)
I believe the answer is:
pressie
'gift' is the definition.
(short for 'present')
'item oddly with jam on top' is the wordplay.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'with' means one lot of letters go next to another.
'jam on top' becomes 'press' (I can't explain this - if you can you should give a lot more credence to this answer).
The alternating letters of 'item' are 'ie'.
'ie' after 'press' is 'PRESSIE'.
Can you help me to learn more?
(Other definitions for pressie that I've seen before include "Gift (colloq.)" , "Something freely given" , "Informally, offering" .)