At back of the science room speak to give more details (9)
I believe the answer is:
elaborate
'give more details' is the definition.
(I've seen this before)
'at back of the science room speak' is the wordplay.
'at' says to put letters next to each other.
'back of' says to take the final letters.
'science room' becomes 'lab' (I've seen this before).
'speak' becomes 'orate' (I've seen this before).
The last letter of 'the' is 'e'.
'e' put next to 'lab' is 'elab'.
'elab'+'orate'='ELABORATE'
'to' acts as a link.
(Other definitions for elaborate that I've seen before include "Expand (upon)" , "Complicated or fancy" , "flesh out?" , "Present in further detail" , "Fussy" .)