Give son something to write with (4)
I believe the answer is:
sink
'give' is the definition.
(as in to give out, collapse)
'son something to write with' is the wordplay.
'son' becomes 's'.
'something to write with' becomes 'ink'.
's'+'ink'='SINK'
(Other definitions for sink that I've seen before include "Dig as for well" , "Succeed in putting" , "Basin - scupper" , "Pocket (billiards)" , "Basin for washing up etc" .)