Remove hair extensions, initially, before short exercise class (7)
I believe the answer is:
Here is my best explanation:
'remove hair' is the definition.
'extensions initially before short exercise class' is the wordplay.
'initially' suggests taking the first letters.
'before' is a charade indicator (letters next to each other).
'short' means to remove the last letter.
'exercise class' becomes 'pilates' (type of exercise class).
The first letter of 'extensions' is 'e'.
'pilates' with its last letter taken off is 'pilate'.