First male worker was unyielding (7)
I believe the answer is:
adamant
'unyielding' is the definition.
(I've seen this before)
'first male worker' is the wordplay.
'first male' becomes 'adam'.
'worker' becomes 'ant' (worker is a type of ant).
'adam'+'ant'='ADAMANT'
'was' is the link.
(Other definitions for adamant that I've seen before include "Fully determined" , "Obdurate and unyielding" , "Inflexible: fabulously hard rock" , "Refusing to budge" , "Firm and unyielding" .)