Lengthways on a pine (5)
I believe the answer is:
along
'lengthways' is the definition.
(thesaurus)
'on a pine' is the wordplay.
'on' says to put letters next to each other.
'pine' becomes 'long' (to pine for something is to long for it).
'a' next to 'long' is 'ALONG'.
(Other definitions for along that I've seen before include "From one end to the other" , "Throughout; onward" , "For the length of" , "Moving in a constant direction on (something)" , "(Going) in company (with others)" .)