In bottom position? That makes Bert alert (5)
I believe the answer is:
basal
'in bottom' is the definition.
'basal' can be an answer for 'bottom' (thesaurus). I am unsure of the 'in' bit.
'position? that makes bert alert' is the wordplay.
I cannot really understand how this works, but
'bert' could be 'al' (both are short for Albert) and 'al' is located in the answer.
The remaining letters 'bas' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for basal that I've seen before include "forming a foundation" , "Fundamental" , "bottom layer perhaps" , "At the lowest level" .)