Pit worker needs a large fizzy drink (7)
I believe the answer is:
mineral
'fizzy drink' is the definition.
'mineral' can be an answer for 'drink' (I've seen this before). I'm not certain of the 'fizzy' bit.
'pit worker needs a large' is the wordplay.
'pit worker' becomes 'miner' (miners work down pits).
'needs' says to put letters next to each other.
'large' becomes 'L' (eg in clothes sizes).
'miner'+'a'+'l'='MINERAL'
Can you help me to learn more?
(Other definitions for mineral that I've seen before include "Substance needed for health; ore" , "What drink is available in ground" , "Metal ore" , "Ore; soft drink" , "Such as 1 dn" .)