Sounds from pen-tip of biro, using pen (7)
I believe the answer is:
oinking
'sounds from pen-tip of biro using pen' is the definition.
I can't judge whether this defines the answer.
'tip of biro using pen' is the wordplay.
'tip of' indicates one should take the final letters.
'using pen' becomes 'inking' (I am not sure about this - if you are sure you should believe this answer much more).
The last letter of 'biro' is 'o'.
'o'+'inking'='OINKING'
Can you help me to learn more?
(Other definitions for oinking that I've seen before include "farmyard noises" , "Sound from pen" , "Noise from Tamworth" .)