Fit soldier with spirit joining first of troops (7)
I believe the answer is:
tantrum
'fit' is the definition.
(I know that fit can be written as tantrum)
'soldier with spirit joining first of troops' is the wordplay.
'soldier' becomes 'ant' (soldier ant is a type of ant).
'with spirit' becomes 'rum' (alcoholic spirit. I am not sure about the 'with' bit.).
'joining' is a charade indicator (letters next to each other).
'first of troops' becomes 't' (rst letter of 'troops').
'ant'+'rum'='antrum'
'antrum' after 't' is 'TANTRUM'.
Can you help me to learn more?
(Other definitions for tantrum that I've seen before include "Burst of temper" , "throwing this?" , "Frenzy" , "Fit of childish temper" , "Childish display of temper" .)