Scratching head in dismissal in lift (5)
I believe the answer is:
boost
'lift' is the definition.
(boosting is a kind of lifting)
'scratching head in dismissal' is the wordplay.
'head' suggests taking the first letters.
'in' is an insertion indicator.
'dismissal' becomes 'boot' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The first letter of 'scratching' is 's'.
's' placed within 'boot' is 'BOOST'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for boost that I've seen before include "Give hope or support to" , "Shot in the arm" , "Fillip" , "Push upwards, help" , "promotion" .)