A plant Sam has to look out for (6)
I believe the answer is:
sesame
'a plant' is the definition.
(sesame is a kind of plant)
'sam has to look out for' is the wordplay.
'has' says to put letters next to each other.
'to look' becomes 'see'.
'out' means to remove the last letter.
'for' becomes 'e' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'see' with its last letter taken off is 'se'.
'sam' after 'se' is 'sesam'.
'sesam'+'e'='SESAME'
Can you help me to learn more?
(Other definitions for sesame that I've seen before include "Password of the Arabian Nights" , "Plant cultivated for seeds providing oil" , "Plant cultivated for its seeds - opening word?" , "Plant with oil-rich seeds" , "Plant grown for its seeds" .)