It is, by the way, an odd play (5)
I believe the answer is:
strum
'play' is the definition.
(I've seen this before)
'it is by the way an odd' is the wordplay.
'it' becomes 't' (abbreviation. e.g. in 'tis).
'is by' says to put letters next to each other.
'the way' becomes 's' (Compass direction - South).
'an odd' becomes 'rum' (rum can mean strange or dubious).
't' after 's' is 'st'.
'st'+'rum'='STRUM'
(Other definitions for strum that I've seen before include "Play idly on guitar etc" , "Casually play (on a stringed instrument)" , "Play a banjo" , "Play badly on a guitar" , "Play stringed instrument with sweep of hand" .)