Poke around the middle of crossbill's nest (5)
I believe the answer is:
roost
'nest' is the definition.
(I've seen this in another clue)
'poke around the middle of crossbill's' is the wordplay.
'poke' becomes 'prod' (synonyms).
'around' says to take the centre.
'the middle of crossbill' becomes 'ost' (I can't explain this - if you can you should give a lot more credence to this answer).
The middle letters of 'prod' are 'ro'.
'ro'+'ost'='ROOST'
Can you help me to learn more?
(Other definitions for roost that I've seen before include "(Bird) settle for night" , "Settle down (on a branch?)" , "Bird's night spot" , "Hen house; perch" , "Perch where bird sleeps" .)