Initially, pen picked up for some writing (5)
I believe the answer is:
prose
'some writing' is the definition.
(I've seen this in another clue)
'initially pen picked up' is the wordplay.
'initially' suggests taking the first letters.
'picked up' becomes 'rose' (past tense of 'raise').
The initial letter of 'pen' is 'p'.
'p'+'rose'='PROSE'
'for' acts as a link.
(Other definitions for prose that I've seen before include "Ordinary writing" , "Ordinary spoken or written language" , "Writings not in verse" , "Non-verse" , "Not poetry" .)