i-adjective
difficult to obtain; hard to get; tough to do
Used when something is hard to obtain, receive permission for, access, or accomplish. Often implies difficulty due to circumstances or inherent obstacles.
このチケットは取りにくい。
These tickets are hard to get.
彼の許可を取りにくい状況だ。
It's a situation where it's difficult to get his permission.
難しい is a general adjective for 'difficult', while 取りにくい specifically means 'difficult to obtain/achieve' and is a compound of 取る (to take) + にくい (difficult to).
得にくい also means 'hard to obtain', but 取りにくい often implies active effort to take or secure something, whereas 得にくい is more passive.
Compound of 取る (toru, 'to take, obtain') + にくい (nikui, 'difficult to do'). The にくい suffix attaches to the masu-stem of verbs to express difficulty in performing the action.